<s>
A	O
solid-state	B-Device
drive	I-Device
(	O
SSD	B-Device
)	O
is	O
a	O
solid-state	B-Device
storage	I-Device
device	I-Device
that	O
uses	O
integrated	O
circuit	O
assemblies	O
to	O
store	O
data	O
persistently	B-Application
,	O
typically	O
using	O
flash	B-Device
memory	I-Device
,	O
and	O
functioning	O
as	O
secondary	O
storage	O
in	O
the	O
hierarchy	O
of	O
computer	B-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
It	O
is	O
also	O
sometimes	O
called	O
a	O
semiconductor	B-Device
storage	I-Device
device	I-Device
,	O
a	O
solid-state	O
device	O
or	O
a	O
solid-state	B-Device
disk	I-Device
,	O
even	O
though	O
SSDs	B-Device
lack	O
the	O
physical	O
spinning	O
disks	B-Device
and	O
movable	O
read	B-Device
–	I-Device
write	I-Device
heads	I-Device
used	O
in	O
hard	B-Device
disk	I-Device
drives	I-Device
(	O
HDDs	O
)	O
and	O
floppy	B-Device
disks	I-Device
.	O
</s>
<s>
SSD	B-Device
also	O
has	O
rich	O
internal	O
parallelism	O
for	O
data	O
processing	O
.	O
</s>
<s>
In	O
comparison	O
to	O
hard	B-Device
disk	I-Device
drives	I-Device
and	O
similar	O
electromechanical	O
media	O
which	O
use	O
moving	O
parts	O
,	O
SSDs	B-Device
are	O
typically	O
more	O
resistant	O
to	O
physical	O
shock	O
,	O
run	O
silently	O
,	O
and	O
have	O
higher	O
input/output	O
rates	O
and	O
lower	O
latency	B-General_Concept
.	O
</s>
<s>
SSDs	B-Device
store	O
data	O
in	O
semiconductor	O
cells	O
.	O
</s>
<s>
SSD	B-Device
storage	O
devices	O
vary	O
in	O
their	O
properties	O
according	O
to	O
the	O
number	O
of	O
bits	O
stored	O
in	O
each	O
cell	O
,	O
with	O
single-bit	O
cells	O
(	O
"	O
Single	O
Level	O
Cells	O
"	O
or	O
"	O
SLC	O
"	O
)	O
being	O
generally	O
the	O
most	O
reliable	O
,	O
durable	O
,	O
fast	O
,	O
and	O
expensive	O
type	O
,	O
compared	O
with	O
2	O
-	O
and	O
3-bit	O
cells	O
(	O
"	O
Multi-Level	O
Cells/MLC	O
"	O
and	O
"	O
Triple-Level	O
Cells/TLC	O
"	O
)	O
,	O
and	O
finally	O
quad-bit	O
cells	O
(	O
"	O
QLC	O
"	O
)	O
being	O
used	O
for	O
consumer	O
devices	O
that	O
do	O
not	O
require	O
such	O
extreme	O
properties	O
and	O
are	O
the	O
cheapest	O
per	O
gigabyte	O
(	O
GB	O
)	O
of	O
the	O
four	O
.	O
</s>
<s>
In	O
addition	O
,	O
3D	B-Device
XPoint	I-Device
memory	I-Device
(	O
sold	O
by	O
Intel	O
under	O
the	O
Optane	O
brand	O
)	O
stores	O
data	O
by	O
changing	O
the	O
electrical	O
resistance	O
of	O
cells	O
instead	O
of	O
storing	O
electrical	O
charges	O
in	O
cells	O
,	O
and	O
SSDs	B-Device
made	O
from	O
RAM	B-Architecture
can	O
be	O
used	O
for	O
high	O
speed	O
,	O
when	O
data	O
persistence	B-Application
after	O
power	O
loss	O
is	O
not	O
required	O
,	O
or	O
may	O
use	O
battery	O
power	O
to	O
retain	O
data	O
when	O
its	O
usual	O
power	O
source	O
is	O
unavailable	O
.	O
</s>
<s>
Hybrid	B-Device
drives	I-Device
or	O
solid-state	B-Device
hybrid	I-Device
drives	I-Device
(	O
SSHDs	B-Device
)	O
,	O
such	O
as	O
Intel	O
's	O
Hystor	O
and	O
Apple	O
's	O
Fusion	B-Device
Drive	I-Device
,	O
combine	O
features	O
of	O
SSDs	B-Device
and	O
HDDs	O
in	O
the	O
same	O
unit	O
using	O
both	O
flash	B-Device
memory	I-Device
and	O
spinning	O
magnetic	B-Architecture
disks	I-Architecture
in	O
order	O
to	O
improve	O
the	O
performance	O
of	O
frequently-accessed	O
data	O
.	O
</s>
<s>
Bcache	B-Application
achieves	O
a	O
similar	O
effect	O
purely	O
in	O
software	O
,	O
using	O
combinations	O
of	O
dedicated	O
regular	O
SSDs	B-Device
and	O
HDDs	O
.	O
</s>
<s>
SSDs	B-Device
based	O
on	O
NAND	O
flash	O
will	O
slowly	O
leak	O
charge	O
over	O
time	O
if	O
left	O
for	O
long	O
periods	O
without	O
power	O
.	O
</s>
<s>
Therefore	O
,	O
SSDs	B-Device
are	O
not	O
suitable	O
for	O
archival	B-General_Concept
storage	I-General_Concept
.	O
</s>
<s>
3D	B-Device
XPoint	I-Device
is	O
a	O
possible	O
exception	O
to	O
this	O
rule	O
;	O
it	O
is	O
a	O
relatively	O
new	O
technology	O
with	O
unknown	O
long-term	O
data-retention	O
characteristics	O
.	O
</s>
<s>
SSDs	B-Device
can	O
use	O
traditional	O
HDD	B-Device
interfaces	O
and	O
form	O
factors	O
,	O
or	O
newer	O
interfaces	O
and	O
form	O
factors	O
that	O
exploit	O
specific	O
advantages	O
of	O
the	O
flash	B-Device
memory	I-Device
in	O
SSDs	B-Device
.	O
</s>
<s>
SATA	O
and	O
SAS	O
)	O
and	O
standard	B-Architecture
HDD	I-Architecture
form	I-Architecture
factors	I-Architecture
allow	O
such	O
SSDs	B-Device
to	O
be	O
used	O
as	O
drop-in	O
replacements	O
for	O
HDDs	O
in	O
computers	O
and	O
other	O
devices	O
.	O
</s>
<s>
Newer	O
form	O
factors	O
such	O
as	O
mSATA	O
,	O
M.2	B-Protocol
,	O
U.2	B-Protocol
,	O
NF1/M.3/NGSFF	O
,	O
XFM	O
Express	O
(	O
Crossover	O
Flash	B-Device
Memory	I-Device
,	O
form	O
factor	O
XT2	O
)	O
and	O
EDSFF	O
(	O
formerly	O
known	O
as	O
Ruler	O
SSD	B-Device
)	O
and	O
higher	O
speed	O
interfaces	O
such	O
as	O
NVM	B-Application
Express	I-Application
(	O
NVMe	B-Application
)	O
over	O
PCI	O
Express	O
(	O
PCIe	O
)	O
can	O
further	O
increase	O
performance	O
over	O
HDD	B-Device
performance	O
.	O
</s>
<s>
SSDs	B-Device
have	O
a	O
limited	O
lifetime	O
number	O
of	O
writes	O
,	O
and	O
also	O
slow	O
down	O
as	O
they	O
reach	O
their	O
full	O
storage	B-General_Concept
capacity	I-General_Concept
.	O
</s>
<s>
An	O
early	O
—	O
if	O
not	O
the	O
first	O
—	O
semiconductor	B-Device
storage	I-Device
device	I-Device
compatible	O
with	O
a	O
hard	B-Device
drive	I-Device
interface	O
(	O
e.g.	O
</s>
<s>
an	O
SSD	B-Device
as	O
defined	O
)	O
was	O
the	O
1978	O
StorageTek	B-Application
STC	O
4305	O
,	O
a	O
plug-compatible	O
replacement	O
for	O
the	O
IBM	B-Device
2305	I-Device
fixed	O
head	O
disk	O
drive	O
.	O
</s>
<s>
It	O
initially	O
used	O
charge-coupled	B-Algorithm
devices	I-Algorithm
(	O
CCDs	O
)	O
for	O
storage	O
(	O
later	O
switched	O
to	O
DRAM	O
)	O
,	O
and	O
consequently	O
was	O
reported	O
to	O
be	O
seven	O
times	O
faster	O
than	O
the	O
IBM	O
product	O
at	O
about	O
half	O
the	O
price	O
( $	O
400,000	O
for	O
45MB	O
capacity	O
)	O
.	O
</s>
<s>
Before	O
the	O
StorageTek	B-Application
SSD	B-Device
there	O
were	O
many	O
DRAM	O
and	O
core	O
(	O
e.g.	O
</s>
<s>
DATARAM	O
BULK	O
Core	O
,	O
1976	O
)	O
products	O
sold	O
as	O
alternatives	O
to	O
HDDs	O
but	O
they	O
typically	O
had	O
memory	O
interfaces	O
and	O
were	O
not	O
SSDs	B-Device
as	O
defined	O
.	O
</s>
<s>
In	O
the	O
late	O
1980s	O
,	O
Zitel	O
offered	O
a	O
family	O
of	O
DRAM	O
based	O
SSD	B-Device
products	O
under	O
the	O
trade	O
name	O
"	O
RAMDisk	B-Application
"	O
,	O
for	O
use	O
on	O
systems	O
by	O
UNIVAC	O
and	O
Perkin-Elmer	O
,	O
among	O
others	O
.	O
</s>
<s>
+	O
SSD	B-Device
evolution	O
Parameter	O
Started	O
with	O
Developed	O
to	O
Improvement	O
Capacity	O
20	O
MB	O
(	O
Sandisk	O
,	O
1991	O
)	O
100	O
TB	O
(	O
Enterprise	O
Nimbus	O
Data	O
DC100	O
,	O
2018	O
)	O
(	O
As	O
of	O
2023	O
up	O
to	O
15.3	O
TB	O
available	O
for	O
consumers	O
)	O
5-million-to-one100	O
,	O
000,000,000,000	O
divided	O
by	O
20,000,000	O
.	O
</s>
<s>
(	O
400,000	O
-to-one	O
)	O
Sequential	O
read	O
speed	O
49.3	O
MB/s	O
(	O
Samsung	O
MCAQE32G5APP-0XA	O
,	O
2007	O
)	O
15	O
GB/s	O
(	O
Gigabyte	O
demonstration	O
,	O
2019	O
)	O
(	O
up	O
to	O
6.795	O
GB/s	O
available	O
for	O
consumers	O
)	O
304.25-to-one15	O
,	O
000÷	O
49.3	O
)	O
(	O
138-to-one	O
)	O
6,795	O
÷	O
49.3	O
,	O
rounded	O
Sequential	O
write	O
speed	O
80	O
MB/s	O
(	O
Samsung	O
enterprise	O
SSD	B-Device
,	O
2008	O
)	O
15.200	O
GB/s	O
(	O
Gigabyte	O
demonstration	O
,	O
2019	O
)	O
(	O
up	O
to	O
4.397	O
GB/s	O
available	O
for	O
consumers	O
)	O
190-to-one15	O
,	O
200÷80	O
(	O
55-to-one	O
)	O
4,397	O
÷80	O
,	O
roundedIOPS	O
79	O
(	O
Samsung	O
MCAQE32G5APP-0XA	O
,	O
2007	O
)	O
2,500,000	O
(	O
Enterprise	O
Micron	O
X100	O
,	O
2019	O
)	O
(	O
up	O
to	O
736,270	O
read	O
IOPS	O
and	O
702,210	O
write	O
IOPS	O
available	O
for	O
consumers	O
)	O
31,645	O
.56-to-one2	O
,	O
500,000	O
÷79	O
(	O
Consumer	O
:	O
read	O
IOPS	O
:	O
9,319	O
.87-to-one	O
,	O
736,270	O
÷79	O
write	O
IOPS	O
:	O
8,888	O
.73-to-one	O
)	O
702,210	O
÷79	O
Access	O
time	O
(	O
in	O
milliseconds	O
,	O
ms	O
)	O
0.5	O
(	O
Samsung	O
MCAQE32G5APP-0XA	O
,	O
2007	O
)	O
0.045	O
read	O
,	O
0.013	O
write	O
(	O
lowest	O
values	O
,	O
WD	O
Black	O
SN850	O
1TB	O
,	O
2020	O
)	O
Read:11-to-one	O
,	O
0.5	O
÷	O
0.045	O
Write	O
:	O
38-to-one0.5	O
÷	O
0.013	O
Price	O
US$	O
50,000	O
per	O
gigabyte	O
(	O
Sandisk	O
,	O
1991	O
)	O
was	O
20	O
MB	O
for	O
$1000	O
,	O
so	O
20÷1000	O
=	O
50	O
so	O
$50	O
per	O
MB	O
,	O
a	O
GB	O
is	O
1000	O
MB	O
so	O
50×1000	O
=	O
50,000	O
US	O
$0.10	O
per	O
gigabyte	O
(	O
Crucial	O
MX500	O
,	O
July	O
2020	O
)	O
https://web.archive.org/web/20200716072857/https://www.techradar.com/amp/news/cheap-ssd-deals	O
Crucial	O
MX500	O
costs	O
$49.99	O
for	O
500	O
GB	O
,	O
so	O
49.99	O
÷500	O
=	O
0.09998	O
,	O
rounded	O
to	O
two	O
significant	O
figures	O
gives	O
0.10	O
555,555	O
-to-one50	O
,	O
000	O
divided	O
by	O
0.25	O
.	O
</s>
<s>
The	O
basis	O
for	O
flash-based	O
SSDs	B-Device
,	O
flash	B-Device
memory	I-Device
,	O
was	O
invented	O
by	O
Fujio	O
Masuoka	O
at	O
Toshiba	O
in	O
1980	O
and	O
commercialized	O
by	O
Toshiba	O
in	O
1987	O
.	O
</s>
<s>
SanDisk	O
Corporation	O
(	O
then	O
SanDisk	O
)	O
founders	O
Eli	O
Harari	O
and	O
Sanjay	O
Mehrotra	O
,	O
along	O
with	O
Robert	O
D	O
.	O
Norman	O
,	O
saw	O
the	O
potential	O
of	O
flash	B-Device
memory	I-Device
as	O
an	O
alternative	O
to	O
existing	O
hard	B-Device
drives	I-Device
,	O
and	O
filed	O
a	O
patent	O
for	O
a	O
flash-based	O
SSD	B-Device
in	O
1989	O
.	O
</s>
<s>
The	O
first	O
commercial	O
flash-based	O
SSD	B-Device
was	O
shipped	O
by	O
SanDisk	O
in	O
1991	O
.	O
</s>
<s>
It	O
was	O
a	O
20MB	O
SSD	B-Device
in	O
a	O
PCMCIA	B-Architecture
configuration	O
,	O
and	O
sold	O
OEM	O
for	O
around	O
$	O
1,000	O
and	O
was	O
used	O
by	O
IBM	O
in	O
a	O
ThinkPad	B-Operating_System
laptop	O
.	O
</s>
<s>
In	O
1998	O
,	O
SanDisk	O
introduced	O
SSDs	B-Device
in	O
2.5-inch	O
and	O
3.5-inch	O
form	O
factors	O
with	O
PATA	B-Protocol
interfaces	O
.	O
</s>
<s>
In	O
1995	O
,	O
STEC	O
,	O
Inc	O
.	O
entered	O
the	O
flash	B-Device
memory	I-Device
business	O
for	O
consumer	O
electronic	O
devices	O
.	O
</s>
<s>
In	O
1995	O
,	O
M-Systems	O
introduced	O
flash-based	O
solid-state	B-Device
drives	I-Device
as	O
HDD	B-Device
replacements	O
for	O
the	O
military	O
and	O
aerospace	O
industries	O
,	O
as	O
well	O
as	O
for	O
other	O
mission-critical	O
applications	O
.	O
</s>
<s>
These	O
applications	O
require	O
the	O
SSD	B-Device
's	O
ability	O
to	O
withstand	O
extreme	O
shock	O
,	O
vibration	O
,	O
and	O
temperature	O
ranges	O
.	O
</s>
<s>
In	O
1999	O
,	O
BiTMICRO	O
made	O
a	O
number	O
of	O
introductions	O
and	O
announcements	O
about	O
flash-based	O
SSDs	B-Device
,	O
including	O
an	O
18GB	O
3.5-inch	O
SSD	B-Device
.	O
</s>
<s>
In	O
2007	O
,	O
Fusion-io	O
announced	O
a	O
PCIe-based	O
Solid	B-Device
state	I-Device
drive	I-Device
with	O
100,000	O
input/output	O
operations	O
per	O
second	O
(	O
IOPS	O
)	O
of	O
performance	O
in	O
a	O
single	O
card	O
,	O
with	O
capacities	O
up	O
to	O
320GB	O
.	O
</s>
<s>
At	O
Cebit	O
2009	O
,	O
OCZ	O
Technology	O
demonstrated	O
a	O
1TB	O
flash	O
SSD	B-Device
using	O
a	O
PCI	O
Express	O
×8	O
interface	O
.	O
</s>
<s>
In	O
December	O
2009	O
,	O
Micron	O
Technology	O
announced	O
an	O
SSD	B-Device
using	O
a	O
6gigabits	O
per	O
second	O
(	O
Gbit/s	O
)	O
SATA	O
interface	O
.	O
</s>
<s>
In	O
2016	O
,	O
Seagate	O
demonstrated	O
10GB/s	O
sequential	O
read	O
and	O
write	O
speeds	O
from	O
a	O
16-lane	O
PCIe	O
3.0	O
SSD	B-Device
,	O
and	O
a	O
60TB	O
SSD	B-Device
in	O
a	O
3.5-inch	O
form	O
factor	O
.	O
</s>
<s>
Samsung	O
also	O
launched	O
to	O
market	O
a	O
15.36TB	O
SSD	B-Device
with	O
a	O
price	O
tag	O
of	O
US$	O
10,000	O
using	O
a	O
SAS	O
interface	O
,	O
using	O
a	O
2.5-inch	O
form	O
factor	O
but	O
with	O
the	O
thickness	O
of	O
3.5-inch	O
drives	O
.	O
</s>
<s>
This	O
was	O
the	O
first	O
time	O
a	O
commercially	O
available	O
SSD	B-Device
had	O
more	O
capacity	O
than	O
the	O
largest	O
currently	O
available	O
HDD	B-Device
.	O
</s>
<s>
In	O
2018	O
,	O
both	O
Samsung	O
and	O
Toshiba	O
launched	O
30.72TB	O
SSDs	B-Device
using	O
the	O
same	O
2.5-inch	O
form	O
factor	O
but	O
with	O
3.5-inch	O
drive	O
thickness	O
using	O
a	O
SAS	O
interface	O
.	O
</s>
<s>
Samsung	O
introduced	O
an	O
M.2	B-Protocol
NVMe	B-Application
SSD	B-Device
with	O
read	O
speeds	O
of	O
3.5GB/s	O
and	O
write	O
speeds	O
of	O
3.3GB/s	O
.	O
</s>
<s>
A	O
new	O
version	O
of	O
the	O
100TB	O
SSD	B-Device
was	O
launched	O
in	O
2020	O
at	O
a	O
price	O
of	O
US$40	O
,	O
000	O
,	O
with	O
the	O
50	O
TB	O
version	O
costing	O
US$	O
12,500	O
.	O
</s>
<s>
In	O
2019	O
,	O
Gigabyte	O
Technology	O
demonstrated	O
an	O
8	O
TB	O
16-lane	O
PCIe	O
4.0	O
SSD	B-Device
with	O
15.0GB/s	O
sequential	O
read	O
and	O
15.2GB/s	O
sequential	O
write	O
speeds	O
at	O
Computex	O
2019	O
.	O
</s>
<s>
It	O
included	O
a	O
fan	B-Application
,	O
as	O
new	O
,	O
high	O
speed	O
SSDs	B-Device
run	O
at	O
high	O
temperatures	O
.	O
</s>
<s>
Also	O
in	O
2019	O
,	O
NVMe	B-Application
M.2	B-Protocol
SSDs	I-Protocol
using	O
the	O
PCIe	O
4.0	O
interface	O
were	O
launched	O
.	O
</s>
<s>
These	O
SSDs	B-Device
have	O
read	O
speeds	O
of	O
up	O
to	O
5.0	O
GB/s	O
and	O
write	O
speeds	O
of	O
up	O
to	O
4.4	O
GB/s	O
.	O
</s>
<s>
Due	O
to	O
their	O
high	O
speed	O
operation	O
,	O
these	O
SSDs	B-Device
use	O
large	O
heatsinks	O
and	O
,	O
without	O
sufficient	O
cooling	O
airflow	O
,	O
will	O
typically	O
thermally	O
throttle	O
down	O
after	O
roughly	O
15	O
minutes	O
of	O
continuous	O
operation	O
at	O
full	O
speed	O
.	O
</s>
<s>
Samsung	O
also	O
introduced	O
SSDs	B-Device
capable	O
of	O
8	O
GB/s	O
sequential	O
read	O
and	O
write	O
speeds	O
and	O
1.5	O
million	O
IOPS	O
,	O
capable	O
of	O
moving	O
data	O
from	O
damaged	O
chips	O
to	O
undamaged	O
chips	O
,	O
to	O
allow	O
the	O
SSD	B-Device
to	O
continue	O
working	O
normally	O
,	O
albeit	O
at	O
a	O
lower	O
capacity	O
.	O
</s>
<s>
In	O
most	O
cases	O
,	O
an	O
EFD	O
is	O
an	O
SSD	B-Device
with	O
a	O
higher	O
set	O
of	O
specifications	O
,	O
compared	O
with	O
SSDs	B-Device
that	O
would	O
typically	O
be	O
used	O
in	O
notebook	O
computers	O
.	O
</s>
<s>
The	O
term	O
was	O
first	O
used	O
by	O
EMC	O
in	O
January	O
2008	O
,	O
to	O
identify	O
SSD	B-Device
manufacturers	I-Device
who	O
would	O
provide	O
products	O
meeting	O
these	O
higher	O
standards	O
.	O
</s>
<s>
There	O
are	O
no	O
standards	O
bodies	O
who	O
control	O
the	O
definition	O
of	O
EFDs	O
,	O
so	O
any	O
SSD	B-Device
manufacturer	O
may	O
claim	O
to	O
produce	O
EFDs	O
when	O
in	O
fact	O
the	O
product	O
may	O
not	O
meet	O
any	O
particular	O
requirements	O
.	O
</s>
<s>
An	O
example	O
is	O
the	O
Intel	O
DCS3700	O
series	O
of	O
drives	O
introduced	O
in	O
the	O
fourth	O
quarter	O
of	O
2012	O
,	O
which	O
focuses	O
on	O
achieving	O
consistent	O
performance	O
,	O
an	O
area	O
that	O
had	O
not	O
received	O
much	O
attention	O
but	O
which	O
Intel	O
claimed	O
was	O
important	O
for	O
the	O
enterprise	O
market	O
;	O
In	O
particular	O
,	O
Intel	O
claims	O
that	O
,	O
at	O
a	O
steady	O
state	O
,	O
the	O
S3700	O
drives	O
would	O
not	O
vary	O
their	O
IOPS	O
by	O
more	O
than	O
10	O
–	O
15%	O
,	O
and	O
that	O
99.9	O
%	O
of	O
all	O
4KB	O
random	O
I/Os	O
are	O
serviced	O
in	O
less	O
than	O
500µs	O
.	O
</s>
<s>
Another	O
example	O
is	O
the	O
Toshiba	O
PX02SS	O
enterprise	O
SSD	B-Device
series	O
announced	O
in	O
2016	O
,	O
optimized	O
for	O
use	O
in	O
server	O
and	O
storage	O
platforms	O
requiring	O
high	O
endurance	O
from	O
write-intensive	O
applications	O
such	O
as	O
write	O
caching	B-General_Concept
,	O
I/O	O
acceleration	O
,	O
and	O
online	B-General_Concept
transaction	I-General_Concept
processing	I-General_Concept
(	O
OLTP	B-General_Concept
)	O
.	O
</s>
<s>
The	O
PX02SS	O
series	O
uses	O
12Gbit/s	O
SAS	O
interface	O
,	O
featuring	O
MLC	B-Device
NAND	O
flash	B-Device
memory	I-Device
and	O
achieving	O
random	B-General_Concept
write	I-General_Concept
speeds	O
of	O
up	O
to	O
42,000	O
IOPS	O
,	O
random	B-General_Concept
read	I-General_Concept
speeds	O
of	O
up	O
to	O
130,000	O
IOPS	O
,	O
and	O
endurance	O
rating	O
of	O
30	O
drive	O
writes	O
per	O
day	O
(	O
DWPD	O
)	O
.	O
</s>
<s>
SSDs	B-Device
based	O
on	O
3D	B-Device
XPoint	I-Device
have	O
higher	O
IOPS	O
(	O
up	O
to	O
2.5	O
million	O
)	O
but	O
lower	O
sequential	O
read/write	O
speeds	O
than	O
their	O
NAND-flash	O
counterparts	O
.	O
</s>
<s>
In	O
2017	O
,	O
the	O
first	O
products	O
with	O
3D	B-Device
XPoint	I-Device
memory	I-Device
were	O
released	O
under	O
Intel	O
's	O
Optane	O
brand	O
;	O
3D	B-Device
Xpoint	I-Device
is	O
entirely	O
different	O
from	O
NAND	O
flash	O
and	O
stores	O
data	O
using	O
different	O
principles	O
.	O
</s>
<s>
The	O
key	O
components	O
of	O
an	O
SSD	B-Device
are	O
the	O
controller	O
and	O
the	O
memory	O
to	O
store	O
the	O
data	O
.	O
</s>
<s>
The	O
primary	O
memory	O
component	O
in	O
an	O
SSD	B-Device
was	O
traditionally	O
DRAM	O
volatile	B-General_Concept
memory	I-General_Concept
,	O
but	O
since	O
2009	O
,	O
it	O
is	O
more	O
commonly	O
NAND	O
flash	O
non-volatile	B-General_Concept
memory	I-General_Concept
.	O
</s>
<s>
Every	O
SSD	B-Device
includes	O
a	B-Device
controller	I-Device
that	O
incorporates	O
the	O
electronics	O
that	O
bridge	O
the	O
NAND	B-Device
memory	I-Device
components	O
to	O
the	O
host	O
computer	O
.	O
</s>
<s>
The	O
controller	O
is	O
an	O
embedded	B-Architecture
processor	I-Architecture
that	O
executes	O
firmware-level	O
code	O
and	O
is	O
one	O
of	O
the	O
most	O
important	O
factors	O
of	O
SSD	B-Device
performance	O
.	O
</s>
<s>
The	O
performance	O
of	O
an	O
SSD	B-Device
can	O
scale	O
with	O
the	O
number	O
of	O
parallel	O
NAND	O
flash	B-Device
chips	I-Device
used	O
in	O
the	O
device	O
.	O
</s>
<s>
A	O
single	O
NAND	O
chip	O
is	O
relatively	O
slow	O
,	O
due	O
to	O
the	O
narrow	O
(	O
8/16bit	O
)	O
asynchronous	B-Architecture
I/O	I-Architecture
interface	O
,	O
and	O
additional	O
high	O
latency	B-General_Concept
of	O
basic	O
I/O	O
operations	O
(	O
typical	O
for	O
SLC	O
NAND	O
,	O
~	O
25μs	O
to	O
fetch	O
a	O
4KiB	O
page	O
from	O
the	O
array	O
to	O
the	O
I/O	O
buffer	O
on	O
a	O
read	O
,	O
~	O
250μs	O
to	O
commit	O
a	O
4KiB	O
page	O
from	O
the	O
IO	O
buffer	O
to	O
the	O
array	O
on	O
a	O
write	O
,	O
~	O
2ms	O
to	O
erase	O
a	O
256KiB	O
block	O
)	O
.	O
</s>
<s>
When	O
multiple	O
NAND	O
devices	O
operate	O
in	O
parallel	O
inside	O
an	O
SSD	B-Device
,	O
the	O
bandwidth	O
scales	O
,	O
and	O
the	O
high	O
latencies	O
can	O
be	O
hidden	O
,	O
as	O
long	O
as	O
enough	O
outstanding	O
operations	O
are	O
pending	O
and	O
the	O
load	O
is	O
evenly	O
distributed	O
between	O
devices	O
.	O
</s>
<s>
Micron	O
and	O
Intel	O
initially	O
made	O
faster	O
SSDs	B-Device
by	O
implementing	O
data	B-General_Concept
striping	I-General_Concept
(	O
similar	O
to	O
RAID	B-Architecture
0	O
)	O
and	O
interleaving	B-General_Concept
in	O
their	O
architecture	O
.	O
</s>
<s>
This	O
enabled	O
the	O
creation	O
of	O
SSDs	B-Device
with	O
250MB/s	O
effective	O
read/write	O
speeds	O
with	O
the	O
SATA	O
3Gbit/s	O
interface	O
in	O
2009	O
.	O
</s>
<s>
Two	O
years	O
later	O
,	O
SandForce	O
continued	O
to	O
leverage	O
this	O
parallel	O
flash	O
connectivity	O
,	O
releasing	O
consumer-grade	O
SATA	O
6Gbit/s	O
SSD	B-Device
controllers	I-Device
which	O
supported	O
500MB/s	O
read/write	O
speeds	O
.	O
</s>
<s>
SandForce	O
controllers	O
compress	O
the	O
data	O
before	O
sending	O
it	O
to	O
the	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
If	O
a	O
particular	O
block	O
is	O
programmed	O
and	O
erased	O
repeatedly	O
without	O
writing	O
to	O
any	O
other	O
blocks	O
,	O
that	O
block	O
will	O
wear	O
out	O
before	O
all	O
the	O
other	O
blocks	O
—	O
thereby	O
prematurely	O
ending	O
the	O
life	O
of	O
the	O
SSD	B-Device
.	O
</s>
<s>
For	O
this	O
reason	O
,	O
SSD	B-Device
controllers	I-Device
use	O
a	O
technique	O
called	O
wear	B-Application
leveling	I-Application
to	O
distribute	O
writes	O
as	O
evenly	O
as	O
possible	O
across	O
all	O
the	O
flash	O
blocks	O
in	O
the	O
SSD	B-Device
.	O
</s>
<s>
Relocating	O
data	O
increases	O
write	B-Error_Name
amplification	I-Error_Name
and	O
adds	O
to	O
the	O
wear	O
of	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
+	O
Comparison	O
of	O
architecturesSLC	O
and	O
MLC	B-Device
SSD	B-Device
Festplatten	O
.	O
</s>
<s>
Most	O
SSD	B-Device
manufacturers	I-Device
use	O
non-volatile	B-General_Concept
NAND	O
flash	B-Device
memory	I-Device
in	O
the	O
construction	O
of	O
their	O
SSDs	B-Device
because	O
of	O
the	O
lower	O
cost	O
compared	O
with	O
DRAM	O
and	O
the	O
ability	O
to	O
retain	O
the	O
data	O
without	O
a	O
constant	O
power	O
supply	O
,	O
ensuring	O
data	O
persistence	B-Application
through	O
sudden	O
power	O
outages	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
SSDs	B-Device
were	O
initially	O
slower	O
than	O
DRAM	O
solutions	O
,	O
and	O
some	O
early	O
designs	O
were	O
even	O
slower	O
than	O
HDDs	O
after	O
continued	O
use	O
.	O
</s>
<s>
Flash-based	O
SSDs	B-Device
store	O
data	O
in	O
metal	B-Architecture
–	I-Architecture
oxide	I-Architecture
–	I-Architecture
semiconductor	I-Architecture
(	O
MOS	O
)	O
integrated	O
circuit	O
chips	O
which	O
contain	O
non-volatile	B-General_Concept
floating-gate	B-Algorithm
memory	B-Algorithm
cells	I-Algorithm
.	O
</s>
<s>
Flash	O
memory-based	O
solutions	O
are	O
typically	O
packaged	O
in	O
standard	O
disk	O
drive	O
form	O
factors	O
(	O
1.8-	O
,	O
2.5-	O
,	O
and	O
3.5-inch	O
)	O
,	O
but	O
also	O
in	O
smaller	O
more	O
compact	O
form	O
factors	O
,	O
such	O
as	O
the	O
M.2	B-Protocol
form	O
factor	O
,	O
made	O
possible	O
by	O
the	O
small	O
size	O
of	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
Lower-priced	O
drives	O
usually	O
use	O
quad-level	O
cell	O
(	O
QLC	O
)	O
,	O
triple-level	O
cell	O
(	O
TLC	O
)	O
or	O
multi-level	B-Device
cell	I-Device
(	O
MLC	B-Device
)	O
flash	B-Device
memory	I-Device
,	O
which	O
is	O
slower	O
and	O
less	O
reliable	O
than	O
single-level	O
cell	O
(	O
SLC	O
)	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
This	O
can	O
be	O
mitigated	O
or	O
even	O
reversed	O
by	O
the	O
internal	O
design	O
structure	O
of	O
the	O
SSD	B-Device
,	O
such	O
as	O
interleaving	B-General_Concept
,	O
changes	O
to	O
writing	O
algorithms	O
,	O
and	O
higher	O
over-provisioning	O
(	O
more	O
excess	O
capacity	O
)	O
with	O
which	O
the	O
wear-leveling	B-Application
algorithms	O
can	O
work	O
.	O
</s>
<s>
Solid-state	B-Device
drives	I-Device
that	O
rely	O
on	O
V-NAND	O
technology	O
,	O
in	O
which	O
layers	O
of	O
cells	O
are	O
stacked	O
vertically	O
,	O
have	O
been	O
introduced	O
.	O
</s>
<s>
SSDs	B-Device
based	O
on	O
volatile	B-General_Concept
memory	I-General_Concept
such	O
as	O
DRAM	O
are	O
characterized	O
by	O
very	O
fast	O
data	O
access	O
,	O
generally	O
less	O
than	O
10microseconds	O
,	O
and	O
are	O
used	O
primarily	O
to	O
accelerate	O
applications	O
that	O
would	O
otherwise	O
be	O
held	O
back	O
by	O
the	O
latency	B-General_Concept
of	O
flash	O
SSDs	B-Device
or	O
traditional	O
HDDs	O
.	O
</s>
<s>
DRAM-based	O
SSDs	B-Device
usually	O
incorporate	O
either	O
an	O
internal	O
battery	O
or	O
an	O
external	O
AC/DC	O
adapter	O
and	O
backup	B-Protocol
storage	I-Protocol
systems	O
to	O
ensure	O
data	O
persistence	B-Application
while	O
no	O
power	O
is	O
being	O
supplied	O
to	O
the	O
drive	O
from	O
external	O
sources	O
.	O
</s>
<s>
If	O
power	O
is	O
lost	O
,	O
the	O
battery	O
provides	O
power	O
while	O
all	O
information	O
is	O
copied	O
from	O
random	B-Architecture
access	I-Architecture
memory	I-Architecture
(	O
RAM	B-Architecture
)	O
to	O
back-up	B-Protocol
storage	O
.	O
</s>
<s>
When	O
the	O
power	O
is	O
restored	O
,	O
the	O
information	O
is	O
copied	O
back	O
to	O
the	O
RAM	B-Architecture
from	O
the	O
back-up	B-Protocol
storage	O
,	O
and	O
the	O
SSD	B-Device
resumes	O
normal	O
operation	O
(	O
similar	O
to	O
the	O
hibernate	O
function	O
used	O
in	O
modern	O
operating	B-General_Concept
systems	I-General_Concept
)	O
.	O
</s>
<s>
SSDs	B-Device
of	O
this	O
type	O
are	O
usually	O
fitted	O
with	O
DRAM	O
modules	O
of	O
the	O
same	O
type	O
used	O
in	O
regular	O
PCs	B-Device
and	O
servers	B-Application
,	O
which	O
can	O
be	O
swapped	O
out	O
and	O
replaced	O
by	O
larger	O
modules	O
.	O
</s>
<s>
Such	O
as	O
i-RAM	B-Device
,	O
HyperOs	B-Device
HyperDrive	I-Device
,	O
DDRdrive	O
X1	O
,	O
etc	O
.	O
</s>
<s>
Some	O
manufacturers	O
of	O
DRAM	O
SSDs	B-Device
solder	O
the	O
DRAM	O
chips	O
directly	O
to	O
the	O
drive	O
,	O
and	O
do	O
not	O
intend	O
the	O
chips	O
to	O
be	O
swapped	O
out	O
—	O
such	O
as	O
ZeusRAM	O
,	O
Aeon	O
Drive	O
,	O
etc	O
.	O
</s>
<s>
A	O
remote	O
,	O
indirect	O
memory-access	O
disk	O
(	O
RIndMA	O
Disk	O
)	O
uses	O
a	O
secondary	O
computer	O
with	O
a	O
fast	O
network	O
or	O
(	O
direct	O
)	O
Infiniband	B-Architecture
connection	O
to	O
act	O
like	O
a	O
RAM-based	O
SSD	B-Device
,	O
but	O
the	O
new	O
,	O
faster	O
,	O
flash-memory	O
based	O
,	O
SSDs	B-Device
already	O
available	O
in	O
2009	O
are	O
making	O
this	O
option	O
not	O
as	O
cost	O
effective	O
.	O
</s>
<s>
While	O
the	O
price	O
of	O
DRAM	O
continues	O
to	O
fall	O
,	O
the	O
price	O
of	O
Flash	B-Device
memory	I-Device
falls	O
even	O
faster	O
.	O
</s>
<s>
In	O
2015	O
,	O
Intel	O
and	O
Micron	O
announced	O
3D	B-Device
XPoint	I-Device
as	O
a	O
new	O
non-volatile	B-General_Concept
memory	I-General_Concept
technology	O
.	O
</s>
<s>
Intel	O
released	O
the	O
first	O
3D	O
XPoint-based	O
drive	O
(	O
branded	O
as	O
Intel	O
Optane	O
SSD	B-Device
)	O
in	O
March	O
2017	O
starting	O
with	O
a	O
data	O
center	O
product	O
,	O
Intel	O
Optane	O
SSD	B-Device
DC	O
P4800X	O
Series	O
,	O
and	O
following	O
with	O
the	O
client	O
version	O
,	O
Intel	O
Optane	O
SSD	B-Device
900P	O
Series	O
,	O
in	O
October	O
2017	O
.	O
</s>
<s>
Both	O
products	O
operate	O
faster	O
and	O
with	O
higher	O
endurance	O
than	O
NAND-based	O
SSDs	B-Device
,	O
while	O
the	O
areal	B-Device
density	I-Device
is	O
comparable	O
at	O
128gigabits	O
per	O
chip	O
.	O
</s>
<s>
For	O
the	O
price	O
per	O
bit	O
,	O
3D	B-Device
XPoint	I-Device
is	O
more	O
expensive	O
than	O
NAND	O
,	O
but	O
cheaper	O
than	O
DRAM	O
.	O
</s>
<s>
Some	O
SSDs	B-Device
,	O
called	O
NVDIMM	B-Device
or	O
Hyper	O
DIMM	O
devices	O
,	O
use	O
both	O
DRAM	O
and	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
When	O
the	O
power	O
goes	O
down	O
,	O
the	O
SSD	B-Device
copies	O
all	O
the	O
data	O
from	O
its	O
DRAM	O
to	O
flash	O
;	O
when	O
the	O
power	O
comes	O
back	B-Protocol
up	I-Protocol
,	O
the	O
SSD	B-Device
copies	O
all	O
the	O
data	O
from	O
its	O
flash	O
to	O
its	O
DRAM	O
.	O
</s>
<s>
In	O
a	O
somewhat	O
similar	O
way	O
,	O
some	O
SSDs	B-Device
use	O
form	O
factors	O
and	O
buses	O
actually	O
designed	O
for	O
DIMM	O
modules	O
,	O
while	O
using	O
only	O
flash	B-Device
memory	I-Device
and	O
making	O
it	O
appear	O
as	O
if	O
it	O
were	O
DRAM	O
.	O
</s>
<s>
Such	O
SSDs	B-Device
are	O
usually	O
known	O
as	O
ULLtraDIMM	B-Device
devices	O
.	O
</s>
<s>
Drives	O
known	O
as	O
hybrid	B-Device
drives	I-Device
or	O
solid-state	B-Device
hybrid	I-Device
drives	I-Device
(	O
SSHDs	B-Device
)	O
use	O
a	O
hybrid	O
of	O
spinning	O
disks	B-Device
and	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
Some	O
SSDs	B-Device
use	O
magnetoresistive	B-General_Concept
random-access	I-General_Concept
memory	I-General_Concept
(	O
MRAM	B-General_Concept
)	O
for	O
storing	O
data	O
.	O
</s>
<s>
A	O
flash-based	O
SSD	B-Device
typically	O
uses	O
a	O
small	O
amount	O
of	O
DRAM	O
as	O
a	O
volatile	B-General_Concept
cache	B-General_Concept
,	O
similar	O
to	O
the	O
buffers	B-Device
in	O
hard	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
A	O
directory	O
of	O
block	O
placement	O
and	O
wear	B-Application
leveling	I-Application
data	O
is	O
also	O
kept	O
in	O
the	O
cache	B-General_Concept
while	O
the	O
drive	O
is	O
operating	O
.	O
</s>
<s>
One	O
SSD	B-Device
controller	I-Device
manufacturer	O
,	O
SandForce	O
,	O
does	O
not	O
use	O
an	O
external	O
DRAM	O
cache	B-General_Concept
on	O
their	O
designs	O
but	O
still	O
achieves	O
high	O
performance	O
.	O
</s>
<s>
Such	O
an	O
elimination	O
of	O
the	O
external	O
DRAM	O
reduces	O
the	O
power	O
consumption	O
and	O
enables	O
further	O
size	O
reduction	O
of	O
SSDs	B-Device
.	O
</s>
<s>
Another	O
component	O
in	O
higher-performing	O
SSDs	B-Device
is	O
a	O
capacitor	O
or	O
some	O
form	O
of	O
battery	O
,	O
which	O
are	O
necessary	O
to	O
maintain	O
data	O
integrity	O
so	O
the	O
data	O
in	O
the	O
cache	B-General_Concept
can	O
be	O
flushed	O
to	O
the	O
drive	O
when	O
power	O
is	O
lost	O
;	O
some	O
may	O
even	O
hold	O
power	O
long	O
enough	O
to	O
maintain	O
data	O
in	O
the	O
cache	B-General_Concept
until	O
power	O
is	O
resumed	O
.	O
</s>
<s>
In	O
the	O
case	O
of	O
MLC	B-Device
flash	I-Device
memory	O
,	O
a	O
problem	O
called	O
lower	O
page	O
corruption	O
can	O
occur	O
when	O
MLC	B-Device
flash	I-Device
memory	O
loses	O
power	O
while	O
programming	O
an	O
upper	O
page	O
.	O
</s>
<s>
This	O
problem	O
does	O
not	O
exist	O
with	O
SLC	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
Many	O
consumer-class	O
SSDs	B-Device
have	O
built-in	O
capacitors	O
to	O
save	O
at	O
least	O
the	O
FTL	O
mapping	O
table	O
on	O
unexpected	O
power	O
loss	O
;	O
among	O
the	O
examples	O
are	O
the	O
Crucial	O
M500	O
and	O
MX100	O
series	O
,	O
the	O
Intel	O
320	O
series	O
,	O
and	O
the	O
more	O
expensive	O
Intel	O
710	O
and	O
730	O
series	O
.	O
</s>
<s>
Enterprise-class	O
SSDs	B-Device
,	O
such	O
as	O
the	O
Intel	O
DCS3700	O
series	O
,	O
usually	O
have	O
built-in	O
batteries	O
or	O
supercapacitors	O
.	O
</s>
<s>
The	O
host	O
interface	O
is	O
physically	O
a	O
connector	O
with	O
the	O
signalling	O
managed	O
by	O
the	O
SSD	B-Device
's	O
controller	O
.	O
</s>
<s>
SSDs	B-Device
support	O
various	O
logical	O
device	O
interfaces	O
,	O
such	O
as	O
Advanced	O
Host	B-Application
Controller	I-Application
Interface	I-Application
(	O
AHCI	O
)	O
and	O
NVMe	B-Application
.	O
</s>
<s>
Logical	O
device	O
interfaces	O
define	O
the	O
command	O
sets	O
used	O
by	O
operating	B-General_Concept
systems	I-General_Concept
to	O
communicate	O
with	O
SSDs	B-Device
and	O
host	B-Architecture
bus	I-Architecture
adapters	I-Architecture
(	O
HBAs	O
)	O
.	O
</s>
<s>
Traditional	O
HDDs	O
and	O
optical	O
drives	O
are	O
designed	O
around	O
the	O
rotating	O
platter(s )	O
or	O
optical	B-Device
disc	I-Device
along	O
with	O
the	O
spindle	O
motor	O
inside	O
.	O
</s>
<s>
Since	O
an	O
SSD	B-Device
is	O
made	O
up	O
of	O
various	O
interconnected	O
integrated	O
circuits	O
(	O
ICs	O
)	O
and	O
an	O
interface	O
connector	O
,	O
its	O
shape	O
is	O
no	O
longer	O
limited	O
to	O
the	O
shape	O
of	O
rotating	O
media	O
drives	O
.	O
</s>
<s>
Some	O
solid-state	B-Device
storage	I-Device
solutions	O
come	O
in	O
a	O
larger	O
chassis	O
that	O
may	O
even	O
be	O
a	O
rack-mount	O
form	O
factor	O
with	O
numerous	O
SSDs	B-Device
inside	O
.	O
</s>
<s>
For	O
desktop	O
computers	O
with	O
3.5-inch	O
hard	B-Device
disk	I-Device
drive	I-Device
slots	O
,	O
a	O
simple	O
adapter	O
plate	O
can	O
be	O
used	O
to	O
make	O
such	O
a	O
drive	O
fit	O
.	O
</s>
<s>
An	O
SSD	B-Device
can	O
also	O
be	O
completely	O
integrated	O
in	O
the	O
other	O
circuitry	O
of	O
the	O
device	O
,	O
as	O
in	O
the	O
Apple	B-Device
MacBook	I-Device
Air	I-Device
(	O
starting	O
with	O
the	O
fall	O
2010	O
model	O
)	O
.	O
</s>
<s>
,	O
mSATA	O
and	O
M.2	B-Protocol
form	O
factors	O
also	O
gained	O
popularity	O
,	O
primarily	O
in	O
laptops	O
.	O
</s>
<s>
The	O
benefit	O
of	O
using	O
a	O
current	O
HDD	B-Device
form	O
factor	O
would	O
be	O
to	O
take	O
advantage	O
of	O
the	O
extensive	O
infrastructure	O
already	O
in	O
place	O
to	O
mount	O
and	O
connect	O
the	O
drives	O
to	O
the	O
host	O
system	O
.	O
</s>
<s>
For	O
applications	O
where	O
space	O
is	O
at	O
a	O
premium	O
,	O
like	O
for	O
ultrabooks	B-Device
or	O
tablet	B-Device
computers	I-Device
,	O
a	O
few	O
compact	O
form	O
factors	O
were	O
standardized	O
for	O
flash-based	O
SSDs	B-Device
.	O
</s>
<s>
It	O
remains	O
electrically	O
compatible	O
with	O
the	O
PCI	O
Express	O
Mini	O
Card	O
interface	O
specification	O
while	O
requiring	O
an	O
additional	O
connection	O
to	O
the	O
SATA	O
host	B-Architecture
controller	I-Architecture
through	O
the	O
same	O
connector	O
.	O
</s>
<s>
M.2	B-Protocol
form	O
factor	O
,	O
formerly	O
known	O
as	O
the	O
Next	B-Protocol
Generation	I-Protocol
Form	I-Protocol
Factor	I-Protocol
(	O
NGFF	B-Protocol
)	O
,	O
is	O
a	O
natural	O
transition	O
from	O
the	O
mSATA	O
and	O
physical	O
layout	O
it	O
used	O
,	O
to	O
a	O
more	O
usable	O
and	O
more	O
advanced	O
form	O
factor	O
.	O
</s>
<s>
While	O
mSATA	O
took	O
advantage	O
of	O
an	O
existing	O
form	O
factor	O
and	O
connector	O
,	O
M.2	B-Protocol
has	O
been	O
designed	O
to	O
maximize	O
usage	O
of	O
the	O
card	O
space	O
,	O
while	O
minimizing	O
the	O
footprint	O
.	O
</s>
<s>
The	O
M.2	B-Protocol
standard	O
allows	O
both	O
SATA	O
and	O
PCI	O
Express	O
SSDs	B-Device
to	O
be	O
fitted	O
onto	O
M.2	B-Protocol
modules	O
.	O
</s>
<s>
Some	O
high	O
performance	O
,	O
high	O
capacity	O
drives	O
uses	O
standard	O
PCI	O
Express	O
add-in	B-Device
card	I-Device
form	O
factor	O
to	O
house	O
additional	O
memory	O
chips	O
,	O
permit	O
the	O
use	O
of	O
higher	O
power	O
levels	O
,	O
and	O
allow	O
the	O
use	O
of	O
a	O
large	O
heat	O
sink	O
.	O
</s>
<s>
There	O
are	O
also	O
adapter	O
boards	O
that	O
converts	O
other	O
form	O
factors	O
,	O
especially	O
M.2	B-Protocol
drives	O
with	O
PCIe	O
interface	O
,	O
into	O
regular	O
add-in	B-Device
cards	I-Device
.	O
</s>
<s>
A	O
disk-on-a-module	O
(	O
DOM	O
)	O
is	O
a	O
flash	O
drive	O
with	O
either	O
40/44	O
-pin	O
Parallel	B-Protocol
ATA	I-Protocol
(	O
PATA	B-Protocol
)	O
or	O
SATA	O
interface	O
,	O
intended	O
to	O
be	O
plugged	O
directly	O
into	O
the	O
motherboard	O
and	O
used	O
as	O
a	O
computer	O
hard	B-Device
disk	I-Device
drive	I-Device
(	O
HDD	B-Device
)	O
.	O
</s>
<s>
DOM	O
devices	O
emulate	O
a	O
traditional	O
hard	B-Device
disk	I-Device
drive	I-Device
,	O
resulting	O
in	O
no	O
need	O
for	O
special	O
drivers	O
or	O
other	O
specific	O
operating	B-General_Concept
system	I-General_Concept
support	O
.	O
</s>
<s>
DOMs	O
are	O
usually	O
used	O
in	O
embedded	B-Architecture
systems	I-Architecture
,	O
which	O
are	O
often	O
deployed	O
in	O
harsh	O
environments	O
where	O
mechanical	O
HDDs	O
would	O
simply	O
fail	O
,	O
or	O
in	O
thin	B-Device
clients	I-Device
because	O
of	O
small	O
size	O
,	O
low	O
power	O
consumption	O
,	O
and	O
silent	O
operation	O
.	O
</s>
<s>
storage	B-General_Concept
capacities	I-General_Concept
range	O
from	O
4MB	O
to	O
128GB	O
with	O
different	O
variations	O
in	O
physical	O
layouts	O
,	O
including	O
vertical	O
or	O
horizontal	O
orientation	O
.	O
</s>
<s>
The	O
number	O
of	O
DRAM	O
components	O
required	O
to	O
get	O
sufficient	O
capacity	O
to	O
store	O
the	O
data	O
along	O
with	O
the	O
backup	B-Protocol
power	O
supplies	O
requires	O
a	O
larger	O
space	O
than	O
traditional	O
HDD	B-Device
form	O
factors	O
.	O
</s>
<s>
Form	O
factors	O
which	O
were	O
more	O
common	O
to	O
memory	O
modules	O
are	O
now	O
being	O
used	O
by	O
SSDs	B-Device
to	O
take	O
advantage	O
of	O
their	O
flexibility	O
in	O
laying	O
out	O
the	O
components	O
.	O
</s>
<s>
The	O
SATADIMM	O
from	O
Viking	O
Technology	O
uses	O
an	O
empty	O
DDR3	O
DIMM	O
slot	O
on	O
the	O
motherboard	O
to	O
provide	O
power	O
to	O
the	O
SSD	B-Device
with	O
a	O
separate	O
SATA	O
connector	O
to	O
provide	O
the	O
data	O
connection	O
back	O
to	O
the	O
computer	O
.	O
</s>
<s>
The	O
result	O
is	O
an	O
easy-to-install	O
SSD	B-Device
with	O
a	O
capacity	O
equal	O
to	O
drives	O
that	O
typically	O
take	O
a	O
full	O
2.5-inch	O
drive	B-Device
bay	I-Device
.	O
</s>
<s>
Some	O
SSDs	B-Device
are	O
based	O
on	O
the	O
PCIe	O
form	O
factor	O
and	O
connect	O
both	O
the	O
data	O
interface	O
and	O
power	O
through	O
the	O
PCIe	O
connector	O
to	O
the	O
host	O
.	O
</s>
<s>
These	O
drives	O
can	O
use	O
either	O
direct	O
PCIe	O
flash	B-Device
controllers	I-Device
or	O
a	O
PCIe-to-SATA	O
bridge	O
device	O
which	O
then	O
connects	O
to	O
SATA	O
flash	B-Device
controllers	I-Device
.	O
</s>
<s>
In	O
the	O
early	O
2000s	O
,	O
a	O
few	O
companies	O
introduced	O
SSDs	B-Device
in	O
Ball	B-Algorithm
Grid	I-Algorithm
Array	I-Algorithm
(	O
BGA	O
)	O
form	O
factors	O
,	O
such	O
as	O
M-Systems	O
'	O
(	O
now	O
SanDisk	O
)	O
DiskOnChip	O
and	O
Silicon	O
Storage	B-Application
Technology	I-Application
's	O
NANDrive	O
(	O
now	O
produced	O
by	O
Greenliant	O
Systems	O
)	O
,	O
and	O
Memoright	O
's	O
M1000	O
for	O
use	O
in	O
embedded	B-Architecture
systems	I-Architecture
.	O
</s>
<s>
The	O
main	O
benefits	O
of	O
BGA	O
SSDs	B-Device
are	O
their	O
low	O
power	O
consumption	O
,	O
small	O
chip	O
package	O
size	O
to	O
fit	O
into	O
compact	O
subsystems	O
,	O
and	O
that	O
they	O
can	O
be	O
soldered	O
directly	O
onto	O
a	O
system	O
motherboard	O
to	O
reduce	O
adverse	O
effects	O
from	O
vibration	O
and	O
shock	O
.	O
</s>
<s>
Such	O
embedded	O
drives	O
often	O
adhere	O
to	O
the	O
eMMC	O
and	O
eUFS	B-Device
standards	O
.	O
</s>
<s>
Making	O
a	O
comparison	O
between	O
SSDs	B-Device
and	O
ordinary	O
(	O
spinning	O
)	O
HDDs	O
is	O
difficult	O
.	O
</s>
<s>
Traditional	O
HDD	B-Device
benchmarks	O
tend	O
to	O
focus	O
on	O
the	O
performance	O
characteristics	O
that	O
are	O
poor	O
with	O
HDDs	O
,	O
such	O
as	O
rotational	O
latency	B-General_Concept
and	O
seek	O
time	O
.	O
</s>
<s>
As	O
SSDs	B-Device
do	O
not	O
need	O
to	O
spin	O
or	O
seek	O
to	O
locate	O
data	O
,	O
they	O
may	O
prove	O
vastly	O
superior	O
to	O
HDDs	O
in	O
such	O
tests	O
.	O
</s>
<s>
However	O
,	O
SSDs	B-Device
have	O
challenges	O
with	O
mixed	O
reads	O
and	O
writes	O
,	O
and	O
their	O
performance	O
may	O
degrade	O
over	O
time	O
.	O
</s>
<s>
SSD	B-Device
testing	O
must	O
start	O
from	O
the	O
(	O
in	O
use	O
)	O
full	O
drive	O
,	O
as	O
the	O
new	O
and	O
empty	O
(	O
fresh	O
,	O
out-of-the-box	O
)	O
drive	O
may	O
have	O
much	O
better	O
write	O
performance	O
than	O
it	O
would	O
show	O
after	O
only	O
weeks	O
of	O
use	O
.	O
</s>
<s>
Most	O
of	O
the	O
advantages	O
of	O
solid-state	B-Device
drives	I-Device
over	O
traditional	O
hard	B-Device
drives	I-Device
are	O
due	O
to	O
their	O
ability	O
to	O
access	O
data	O
completely	O
electronically	O
instead	O
of	O
electromechanically	O
,	O
resulting	O
in	O
superior	O
transfer	O
speeds	O
and	O
mechanical	O
ruggedness	O
.	O
</s>
<s>
On	O
the	O
other	O
hand	O
,	O
hard	B-Device
disk	I-Device
drives	I-Device
offer	O
significantly	O
higher	O
capacity	O
for	O
their	O
price	O
.	O
</s>
<s>
Some	O
field	O
failure	O
rates	O
indicate	O
that	O
SSDs	B-Device
are	O
significantly	O
more	O
reliable	O
than	O
HDDs	O
but	O
others	O
do	O
not	O
.	O
</s>
<s>
However	O
,	O
SSDs	B-Device
are	O
uniquely	O
sensitive	O
to	O
sudden	O
power	O
interruption	O
,	O
resulting	O
in	O
aborted	O
writes	O
or	O
even	O
cases	O
of	O
the	O
complete	O
loss	O
of	O
the	O
drive	O
.	O
</s>
<s>
The	O
reliability	O
of	O
both	O
HDDs	O
and	O
SSDs	B-Device
varies	O
greatly	O
among	O
models	O
.	O
</s>
<s>
As	O
with	O
HDDs	O
,	O
there	O
is	O
a	O
tradeoff	O
between	O
cost	O
and	O
performance	O
of	O
different	O
SSDs	B-Device
.	O
</s>
<s>
Single-level	O
cell	O
(	O
SLC	O
)	O
SSDs	B-Device
,	O
while	O
significantly	O
more	O
expensive	O
than	O
multi-level	O
(	O
MLC	B-Device
)	O
SSDs	B-Device
,	O
offer	O
a	O
significant	O
speed	O
advantage	O
.	O
</s>
<s>
At	O
the	O
same	O
time	O
,	O
DRAM-based	O
solid-state	B-Device
storage	I-Device
is	O
currently	O
considered	O
the	O
fastest	O
and	O
most	O
costly	O
,	O
with	O
average	O
response	O
times	O
of	O
10	O
microseconds	O
instead	O
of	O
the	O
average	O
100	O
microseconds	O
of	O
other	O
SSDs	B-Device
.	O
</s>
<s>
Enterprise	O
flash	O
devices	O
(	O
EFDs	O
)	O
are	O
designed	O
to	O
handle	O
the	O
demands	O
of	O
tier-1	O
application	O
with	O
performance	O
and	O
response	O
times	O
similar	O
to	O
less-expensive	O
SSDs	B-Device
.	O
</s>
<s>
In	O
traditional	O
HDDs	O
,	O
a	O
rewritten	O
file	O
will	O
generally	O
occupy	O
the	O
same	O
location	O
on	O
the	O
disk	O
surface	O
as	O
the	O
original	O
file	O
,	O
whereas	O
in	O
SSDs	B-Device
the	O
new	O
copy	O
will	O
often	O
be	O
written	O
to	O
different	O
NAND	O
cells	O
for	O
the	O
purpose	O
of	O
wear	B-Application
leveling	I-Application
.	O
</s>
<s>
The	O
wear-leveling	B-Application
algorithms	O
are	O
complex	O
and	O
difficult	O
to	O
test	O
exhaustively	O
;	O
as	O
a	O
result	O
,	O
one	O
major	O
cause	O
of	O
data	O
loss	O
in	O
SSDs	B-Device
is	O
firmware	O
bugs	O
.	O
</s>
<s>
+	O
Comparison	O
of	O
NAND-based	O
SSD	B-Device
and	O
HDD	B-Device
Attribute	O
or	O
characteristic	O
Solid-state	B-Device
drive	I-Device
Hard	B-Device
disk	I-Device
drive	I-Device
Price	O
per	O
capacity	O
SSDs	B-Device
generally	O
are	O
more	O
expensive	O
than	O
HDDs	O
and	O
expected	O
to	O
remain	O
so	O
into	O
the	O
2020s	O
.	O
</s>
<s>
SSD	B-Device
price	O
is	O
around	O
30	O
cents	O
(	O
US	O
)	O
per	O
gigabyte	O
based	O
on	O
4	O
TB	O
models	O
.	O
</s>
<s>
Prices	O
have	O
generally	O
declined	O
annually	O
and	O
are	O
expected	O
to	O
continue	O
to	O
do	O
so.HDD	O
price	O
is	O
around	O
2	O
to	O
3	O
cents	O
(	O
US	O
)	O
per	O
gigabyte	O
based	O
on	O
1	O
TB	O
models	O
.	O
</s>
<s>
Storage	B-General_Concept
capacity	I-General_Concept
In	O
2018	O
,	O
SSDs	B-Device
were	O
available	O
in	O
sizes	O
up	O
to	O
100	O
TB	O
,	O
but	O
less	O
costly	O
,	O
120	O
to	O
512	O
GB	O
models	O
were	O
more	O
common	O
.	O
</s>
<s>
Reliability	O
–	O
data	O
retention	O
If	O
left	O
without	O
power	O
,	O
worn	O
out	O
SSDs	B-Device
typically	O
start	O
to	O
lose	O
data	O
after	O
about	O
one	O
to	O
two	O
years	O
in	O
storage	O
,	O
depending	O
on	O
temperature	O
.	O
</s>
<s>
MLC	B-Device
and	O
TLC	O
based	O
devices	O
tend	O
to	O
lose	O
data	O
earlier	O
than	O
SLC-based	O
devices	O
.	O
</s>
<s>
SSDs	B-Device
are	O
not	O
suited	O
for	O
archival	O
use	O
.	O
</s>
<s>
Reliability	O
–	O
longevity	O
SSDs	B-Device
have	O
no	O
moving	O
parts	O
to	O
fail	O
mechanically	O
so	O
in	O
theory	O
,	O
should	O
be	O
more	O
reliable	O
than	O
HDDs	O
.	O
</s>
<s>
Each	O
block	O
of	O
a	O
flash-based	O
SSD	B-Device
can	O
only	O
be	O
erased	O
(	O
and	O
therefore	O
written	O
)	O
a	O
limited	O
number	O
of	O
times	O
before	O
it	O
fails	O
.	O
</s>
<s>
The	O
controllers	O
manage	O
this	O
limitation	O
so	O
that	O
drives	O
can	O
last	O
for	O
many	O
years	O
under	O
normal	O
use.Tests	O
by	O
Tom	O
's	O
Hardware	O
on	O
the	O
60	O
GB	O
Intel	O
520	O
SSD	B-Device
calculated	O
a	O
worst-case	O
lifetime	O
of	O
just	O
over	O
five	O
years	O
for	O
incompressible	O
data	O
,	O
and	O
a	O
lifetime	O
of	O
75	O
years	O
for	O
compressible	O
data	O
.	O
</s>
<s>
SSDs	B-Device
based	O
on	O
DRAM	O
do	O
not	O
have	O
a	O
limited	O
number	O
of	O
writes	O
.	O
</s>
<s>
However	O
the	O
failure	O
of	O
a	B-Device
controller	I-Device
can	O
make	O
an	O
SSD	B-Device
unusable	O
.	O
</s>
<s>
Reliability	O
varies	O
significantly	O
across	O
different	O
SSD	B-Device
manufacturers	I-Device
and	O
models	O
with	O
return	O
rates	O
reaching	O
40%	O
for	O
specific	O
drives	O
.	O
</s>
<s>
A	O
Facebook	B-Application
study	O
found	O
that	O
sparse	O
data	O
layout	O
across	O
an	O
SSD	B-Device
's	O
physical	O
address	O
space	O
(	O
e.g.	O
,	O
non-contiguously	O
allocated	O
data	O
)	O
,	O
dense	O
data	O
layout	O
(	O
e.g.	O
,	O
contiguous	B-Architecture
data	O
)	O
and	O
higher	O
operating	O
temperature	O
(	O
which	O
correlates	O
with	O
the	O
power	O
used	O
to	O
transmit	O
data	O
)	O
each	O
lead	O
to	O
increased	O
failure	O
rates	O
among	O
SSDs	B-Device
.	O
</s>
<s>
However	O
,	O
SSDs	B-Device
have	O
undergone	O
many	O
revisions	O
that	O
have	O
made	O
them	O
more	O
reliable	O
and	O
long	O
lasting	O
.	O
</s>
<s>
New	O
SSDs	B-Device
in	O
the	O
market	O
today	O
use	O
power	O
loss	O
protection	O
circuits	O
,	O
wear	B-Application
leveling	I-Application
techniques	O
and	O
thermal	O
throttling	O
to	O
ensure	O
longevity	O
.	O
</s>
<s>
HDDs	O
have	O
moving	O
parts	O
,	O
and	O
are	O
subject	O
to	O
potential	O
mechanical	O
failures	O
from	O
the	O
resulting	O
wear	O
and	O
tear	O
so	O
in	O
theory	O
,	O
should	O
be	O
less	O
reliable	O
than	O
SSDs	B-Device
.	O
</s>
<s>
The	O
storage	O
medium	O
itself	O
(	O
magnetic	O
platter	B-Device
)	O
does	O
not	O
essentially	O
degrade	O
from	O
reading	O
and	O
write	O
operations	O
.	O
</s>
<s>
When	O
stored	O
offline	O
(	O
unpowered	O
on	O
the	O
shelf	O
)	O
in	O
long	O
term	O
,	O
the	O
magnetic	B-Architecture
medium	I-Architecture
of	O
HDD	B-Device
retains	O
data	O
significantly	O
longer	O
than	O
flash	B-Device
memory	I-Device
used	O
in	O
SSDs	B-Device
.	O
</s>
<s>
Drive	O
spin-up	B-Device
may	O
take	O
several	O
seconds	O
.	O
</s>
<s>
A	O
system	O
with	O
many	O
drives	O
may	O
need	O
to	O
stagger	O
spin-up	B-Device
to	O
limit	O
peak	O
power	O
drawn	O
,	O
which	O
is	O
briefly	O
high	O
when	O
an	O
HDD	B-Device
is	O
first	O
started	O
.	O
</s>
<s>
Enterprise	O
SSDs	B-Device
can	O
have	O
multi-gigabyte	O
per	O
second	O
throughput	O
.	O
</s>
<s>
Once	O
the	O
head	O
is	O
positioned	O
,	O
when	O
reading	O
or	O
writing	O
a	O
continuous	O
track	O
,	O
a	O
modern	O
HDD	B-Device
can	O
transfer	O
data	O
at	O
about	O
200	O
MB/s	O
.	O
</s>
<s>
Random	B-General_Concept
access	I-General_Concept
performanceRandom	O
access	O
time	O
typically	O
under	O
0.1	O
ms.	O
As	O
data	O
can	O
be	O
retrieved	O
directly	O
from	O
various	O
locations	O
of	O
the	O
flash	B-Device
memory	I-Device
,	O
access	O
time	O
is	O
usually	O
not	O
a	O
big	O
performance	O
bottleneck	O
.	O
</s>
<s>
In	O
applications	O
,	O
where	O
hard	B-Device
disk	I-Device
drive	I-Device
seeks	O
are	O
the	O
limiting	O
factor	O
,	O
this	O
results	O
in	O
faster	O
boot	B-Operating_System
and	O
application	O
launch	O
times	O
(	O
see	O
Amdahl	B-Operating_System
's	I-Operating_System
law	I-Operating_System
)	O
.	O
</s>
<s>
SSD	B-Device
technology	O
can	O
deliver	O
rather	O
consistent	O
read/write	O
speed	O
,	O
but	O
when	O
many	O
individual	O
smaller	O
blocks	O
are	O
accessed	O
,	O
performance	O
is	O
reduced	O
.	O
</s>
<s>
Flash	B-Device
memory	I-Device
must	O
be	O
erased	O
before	O
it	O
can	O
be	O
rewritten	O
to	O
.	O
</s>
<s>
This	O
requires	O
an	O
excess	O
number	O
of	O
write	O
operations	O
over	O
and	O
above	O
that	O
intended	O
(	O
a	O
phenomenon	O
known	O
as	O
write	B-Error_Name
amplification	I-Error_Name
)	O
,	O
which	O
negatively	O
impacts	O
performance	O
.	O
</s>
<s>
SSDs	B-Device
typically	O
exhibit	O
a	O
small	O
,	O
steady	O
reduction	O
in	O
write	O
performance	O
over	O
their	O
lifetime	O
,	O
although	O
the	O
average	O
write	O
speed	O
of	O
some	O
drives	O
can	O
improve	O
with	O
age	O
.	O
</s>
<s>
Read	O
latency	B-General_Concept
time	O
is	O
much	O
higher	O
than	O
SSDs	B-Device
.	O
</s>
<s>
Random	B-General_Concept
access	I-General_Concept
time	O
ranges	O
from	O
2.9	O
(	O
high	O
end	O
server	O
drive	O
)	O
to	O
12	O
ms	O
(	O
laptop	O
HDD	B-Device
)	O
due	O
to	O
the	O
need	O
to	O
move	O
the	O
heads	B-Device
and	O
wait	O
for	O
the	O
data	O
to	O
rotate	O
under	O
the	O
magnetic	O
head	O
.	O
</s>
<s>
If	O
data	O
from	O
different	O
areas	O
of	O
the	O
platter	B-Device
must	O
be	O
accessed	O
,	O
as	O
with	O
fragmented	O
files	O
,	O
response	O
times	O
will	O
be	O
increased	O
by	O
the	O
need	O
to	O
seek	O
each	O
fragment	O
.	O
</s>
<s>
Impact	O
of	O
file	B-Application
system	I-Application
fragmentation	I-Application
There	O
is	O
limited	O
benefit	O
to	O
reading	O
data	O
sequentially	O
(	O
beyond	O
typical	O
FS	O
block	O
sizes	O
,	O
say	O
4	O
KiB	O
)	O
,	O
making	O
fragmentation	B-Architecture
negligible	O
for	O
SSDs	B-Device
.	O
</s>
<s>
Defragmentation	B-Application
would	O
cause	O
wear	O
by	O
making	O
additional	O
writes	O
of	O
the	O
NAND	O
flash	O
cells	O
,	O
which	O
have	O
a	O
limited	O
cycle	O
life	O
.	O
</s>
<s>
However	O
,	O
even	O
with	O
SSDs	B-Device
there	O
is	O
a	O
practical	O
limit	O
on	O
how	O
much	O
fragmentation	B-Architecture
certain	O
file	B-Application
systems	I-Application
can	O
sustain	O
;	O
once	O
that	O
limit	O
is	O
reached	O
,	O
subsequent	O
file	O
allocations	O
fail	O
.	O
</s>
<s>
Consequently	O
,	O
defragmentation	B-Application
may	O
still	O
be	O
necessary	O
,	O
although	O
to	O
a	O
lesser	O
degree	O
.	O
</s>
<s>
Some	O
file	B-Application
systems	I-Application
,	O
like	O
NTFS	B-Application
,	O
become	O
fragmented	O
over	O
time	O
if	O
frequently	O
written	O
;	O
periodic	O
defragmentation	B-Application
is	O
required	O
to	O
maintain	O
optimum	O
performance	O
.	O
</s>
<s>
Acoustic	O
noise	O
SSDs	B-Device
have	O
no	O
moving	O
parts	O
and	O
therefore	O
are	O
silent	O
,	O
although	O
,	O
on	O
some	O
SSDs	B-Device
,	O
high	O
pitch	O
noise	O
from	O
the	O
high	O
voltage	O
generator	O
(	O
for	O
erasing	O
blocks	O
)	O
may	O
occur	O
.	O
</s>
<s>
HDDs	O
have	O
moving	O
parts	O
(	O
heads	B-Device
,	O
actuator	O
,	O
and	O
spindle	O
motor	O
)	O
and	O
make	O
characteristic	O
sounds	O
of	O
whirring	O
and	O
clicking	O
;	O
noise	O
levels	O
vary	O
depending	O
on	O
the	O
RPM	O
,	O
but	O
can	O
be	O
significant	O
(	O
while	O
often	O
much	O
lower	O
than	O
the	O
sound	O
from	O
the	O
cooling	O
fans	O
)	O
.	O
</s>
<s>
Laptop	B-Device
hard	I-Device
drives	I-Device
are	O
relatively	O
quiet	O
.	O
</s>
<s>
Temperature	O
control	O
A	O
Facebook	B-Application
study	O
found	O
that	O
at	O
operating	O
temperatures	O
above	O
,	O
the	O
failure	O
rate	O
among	O
SSDs	B-Device
increases	O
with	O
temperature	O
.	O
</s>
<s>
In	O
practice	O
,	O
SSDs	B-Device
usually	O
do	O
not	O
require	O
any	O
special	O
cooling	O
and	O
can	O
tolerate	O
higher	O
temperatures	O
than	O
HDDs	O
.	O
</s>
<s>
Some	O
SSDs	B-Device
,	O
including	O
high-end	O
enterprise	O
models	O
installed	O
as	O
add-on	B-Device
cards	I-Device
or	O
2.5-inch	O
bay	O
devices	O
,	O
may	O
ship	O
with	O
heat	O
sinks	O
to	O
dissipate	O
generated	O
heat	O
,	O
requiring	O
certain	O
volumes	O
of	O
airflow	O
to	O
operate	O
.	O
</s>
<s>
Ambient	O
temperatures	O
above	O
can	O
shorten	O
the	O
life	O
of	O
a	O
hard	B-Device
disk	I-Device
,	O
and	O
reliability	O
will	O
be	O
compromised	O
at	O
drive	O
temperatures	O
above	O
.	O
</s>
<s>
Fan	B-Application
cooling	O
may	O
be	O
required	O
if	O
temperatures	O
would	O
otherwise	O
exceed	O
these	O
values	O
.	O
</s>
<s>
Lowest	O
operating	O
temperature	O
SSDs	B-Device
can	O
operate	O
at	O
.	O
</s>
<s>
Highest	O
altitude	O
when	O
operating	O
SSDs	B-Device
have	O
no	O
issues	O
on	O
this	O
.	O
</s>
<s>
Moving	O
from	O
a	O
cold	O
environment	O
to	O
a	O
warmer	O
environment	O
SSDs	B-Device
have	O
no	O
issues	O
with	O
this	O
.	O
</s>
<s>
Due	O
to	O
the	O
thermal	O
throttling	O
mechanism	O
SSDs	B-Device
are	O
kept	O
secure	O
and	O
prevented	O
from	O
the	O
temperature	O
imbalance	O
.	O
</s>
<s>
A	O
certain	O
amount	O
of	O
acclimation	O
time	O
may	O
be	O
needed	O
when	O
moving	O
some	O
HDDs	O
from	O
a	O
cold	O
environment	O
to	O
a	O
warmer	O
environment	O
before	O
operating	O
them	O
;	O
depending	O
upon	O
humidity	O
,	O
condensation	O
could	O
occur	O
on	O
heads	B-Device
and/or	O
disks	B-Device
and	O
operating	O
it	O
immediately	O
will	O
result	O
in	O
damage	O
to	O
such	O
components	O
.	O
</s>
<s>
Breather	O
hole	O
SSDs	B-Device
do	O
not	O
require	O
a	O
breather	O
hole	O
.	O
</s>
<s>
Heads	B-Device
flying	O
above	O
rapidly	O
rotating	O
platters	O
are	O
susceptible	O
to	O
shock	O
,	O
vibration	O
,	O
movement	O
,	O
and	O
contamination	O
which	O
could	O
damage	O
the	O
medium	O
.	O
</s>
<s>
Susceptibility	O
to	O
magnetic	O
fields	O
Low	O
impact	O
on	O
flash	B-Device
memory	I-Device
,	O
but	O
an	O
electromagnetic	O
pulse	O
will	O
damage	O
any	O
electrical	O
system	O
,	O
especially	O
integrated	O
circuits	O
.	O
</s>
<s>
Weight	O
and	O
size	O
SSDs	B-Device
,	O
essentially	O
semiconductor	O
memory	O
devices	O
mounted	O
on	O
a	O
circuit	O
board	O
,	O
are	O
small	O
and	O
lightweight	O
.	O
</s>
<s>
They	O
often	O
follow	O
the	O
same	O
form	O
factors	O
as	O
HDDs	O
(	O
2.5-inch	O
or	O
1.8-inch	O
)	O
or	O
are	O
bare	O
PCBs	O
(	O
M.2	B-Protocol
and	O
mSATA	O
)	O
.	O
</s>
<s>
HDDs	O
are	O
generally	O
heavier	O
than	O
SSDs	B-Device
,	O
as	O
the	O
enclosures	O
are	O
made	O
mostly	O
of	O
metal	O
,	O
and	O
they	O
contain	O
heavy	O
objects	O
such	O
as	O
motors	O
and	O
large	O
magnets	O
.	O
</s>
<s>
Secure	O
writing	O
limitations	O
NAND	O
flash	B-Device
memory	I-Device
cannot	O
be	O
overwritten	O
,	O
but	O
has	O
to	O
be	O
rewritten	O
to	O
previously	O
erased	O
blocks	O
.	O
</s>
<s>
If	O
a	O
software	O
encryption	O
program	O
encrypts	O
data	O
already	O
on	O
the	O
SSD	B-Device
,	O
the	O
overwritten	O
data	O
is	O
still	O
unsecured	O
,	O
unencrypted	O
,	O
and	O
accessible	O
(	O
drive-based	O
hardware	O
encryption	O
does	O
not	O
have	O
this	O
problem	O
)	O
.	O
</s>
<s>
Some	O
manufacturers	O
 '	O
HDDs	O
fill	O
the	O
entire	O
drive	O
with	O
zeroes	O
,	O
including	O
relocated	O
sectors	O
,	O
on	O
ATA	B-Protocol
Secure	O
Erase	O
Enhanced	O
Erase	O
command	O
.	O
</s>
<s>
Read/write	O
performance	O
symmetry	O
Less	O
expensive	O
SSDs	B-Device
typically	O
have	O
write	O
speeds	O
significantly	O
lower	O
than	O
their	O
read	O
speeds	O
.	O
</s>
<s>
Higher	O
performing	O
SSDs	B-Device
have	O
similar	O
read	O
and	O
write	O
speeds	O
.	O
</s>
<s>
Free	O
block	O
availability	O
and	O
TRIM	O
SSD	B-Device
write	O
performance	O
is	O
significantly	O
impacted	O
by	O
the	O
availability	O
of	O
free	O
,	O
programmable	O
blocks	O
.	O
</s>
<s>
Power	O
consumption	O
High	O
performance	O
flash-based	O
SSDs	B-Device
generally	O
require	O
half	O
to	O
a	O
third	O
of	O
the	O
power	O
of	O
HDDs	O
.	O
</s>
<s>
High-performance	O
DRAM	O
SSDs	B-Device
generally	O
require	O
as	O
much	O
power	O
as	O
HDDs	O
,	O
and	O
must	O
be	O
connected	O
to	O
power	O
even	O
when	O
the	O
rest	O
of	O
the	O
system	O
is	O
shut	O
down.	O
|	O
-	O
Emerging	O
technologies	O
like	O
DevSlp	B-Device
can	O
minimize	O
power	O
requirements	O
of	O
idle	O
drives	O
.	O
</s>
<s>
While	O
both	O
memory	B-Device
cards	I-Device
and	O
most	O
SSDs	B-Device
use	O
flash	B-Device
memory	I-Device
,	O
they	O
serve	O
very	O
different	O
markets	O
and	O
purposes	O
.	O
</s>
<s>
SSDs	B-Device
were	O
originally	O
designed	O
for	O
use	O
in	O
a	O
computer	O
system	O
.	O
</s>
<s>
The	O
first	O
units	O
were	O
intended	O
to	O
replace	O
or	O
augment	O
hard	B-Device
disk	I-Device
drives	I-Device
,	O
so	O
the	O
operating	B-General_Concept
system	I-General_Concept
recognized	O
them	O
as	O
a	O
hard	B-Device
drive	I-Device
.	O
</s>
<s>
Originally	O
,	O
solid	B-Device
state	I-Device
drives	I-Device
were	O
even	O
shaped	O
and	O
mounted	O
in	O
the	O
computer	O
like	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
Later	O
SSDs	B-Device
became	O
smaller	O
and	O
more	O
compact	O
,	O
eventually	O
developing	O
their	O
own	O
unique	O
form	O
factors	O
such	O
as	O
the	O
M.2	B-Protocol
form	O
factor	O
.	O
</s>
<s>
The	O
SSD	B-Device
was	O
designed	O
to	O
be	O
installed	O
permanently	O
inside	O
a	O
computer	O
.	O
</s>
<s>
In	O
contrast	O
,	O
memory	B-Device
cards	I-Device
(	O
such	O
as	O
Secure	B-Device
Digital	I-Device
(	O
SD	O
)	O
,	O
CompactFlash	B-Device
(	O
CF	B-Device
)	O
,	O
and	O
many	O
others	O
)	O
were	O
originally	O
designed	O
for	O
digital	O
cameras	O
and	O
later	O
found	O
their	O
way	O
into	O
cell	O
phones	O
,	O
gaming	O
devices	O
,	O
GPS	O
units	O
,	O
etc	O
.	O
</s>
<s>
Most	O
memory	B-Device
cards	I-Device
are	O
physically	O
smaller	O
than	O
SSDs	B-Device
,	O
and	O
designed	O
to	O
be	O
inserted	O
and	O
removed	O
repeatedly	O
.	O
</s>
<s>
SSDs	B-Device
have	O
very	O
different	O
failure	O
modes	O
from	O
traditional	O
magnetic	B-Device
hard	I-Device
drives	I-Device
.	O
</s>
<s>
Because	O
solid-state	B-Device
drives	I-Device
contain	O
no	O
moving	O
parts	O
,	O
they	O
are	O
generally	O
not	O
subject	O
to	O
mechanical	O
failures	O
.	O
</s>
<s>
On	O
the	O
whole	O
,	O
however	O
,	O
studies	O
have	O
shown	O
that	O
SSDs	B-Device
are	O
generally	O
highly	O
reliable	O
,	O
and	O
often	O
continue	O
working	O
far	O
beyond	O
the	O
expected	O
lifetime	O
as	O
stated	O
by	O
their	O
manufacturer	O
.	O
</s>
<s>
The	O
endurance	O
of	O
an	O
SSD	B-Device
should	O
be	O
provided	O
on	O
its	O
datasheet	O
in	O
one	O
of	O
two	O
forms	O
:	O
</s>
<s>
So	O
for	O
example	O
a	O
Samsung	O
970	O
EVO	O
NVMe	B-Application
M.2	B-Protocol
SSD	I-Protocol
(	O
2018	O
)	O
with	O
1TB	O
has	O
an	O
endurance	O
of	O
600TBW	O
.	O
</s>
<s>
An	O
early	O
investigation	O
by	O
Techreport.com	O
that	O
ran	O
from	O
2013	O
to	O
2015	O
involved	O
a	O
number	O
of	O
flash-based	O
SSDs	B-Device
being	O
tested	O
to	O
destruction	O
to	O
identify	O
how	O
and	O
at	O
what	O
point	O
they	O
failed	O
.	O
</s>
<s>
The	O
first	O
SSD	B-Device
to	O
fail	O
was	O
TLC-based	O
,	O
with	O
the	O
drive	O
succeeding	O
in	O
writing	O
over	O
800TB	O
.	O
</s>
<s>
Three	O
SSDs	B-Device
in	O
the	O
test	O
wrote	O
three	O
times	O
that	O
amount	O
(	O
almost	O
2.5	O
PB	O
)	O
before	O
they	O
too	O
failed	O
.	O
</s>
<s>
The	O
test	O
demonstrated	O
the	O
remarkable	O
reliability	O
of	O
even	O
consumer-market	O
SSDs	B-Device
.	O
</s>
<s>
A	O
2016	O
field	O
study	O
based	O
on	O
data	O
collected	O
over	O
six	O
years	O
in	O
Google	B-Application
's	I-Application
data	O
centres	O
and	O
spanning	O
"	O
millions	O
"	O
of	O
drive	O
days	O
found	O
that	O
the	O
proportion	O
of	O
flash-based	O
SSDs	B-Device
requiring	O
replacement	O
in	O
their	O
first	O
four	O
years	O
of	O
use	O
ranged	O
from	O
4%	O
to	O
10%	O
depending	O
on	O
the	O
model	O
.	O
</s>
<s>
The	O
authors	O
concluded	O
that	O
SSDs	B-Device
fail	O
at	O
a	O
significantly	O
lower	O
rate	O
than	O
hard	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
(	O
In	O
contrast	O
,	O
a	O
2016	O
evaluation	O
of	O
71,940	O
HDDs	O
found	O
failure	O
rates	O
comparable	O
to	O
those	O
of	O
Google	B-Application
's	I-Application
SSDs	B-Device
:	O
the	O
HDDs	O
had	O
on	O
average	O
an	O
annualized	O
failure	O
rate	O
of	O
1.95	O
%	O
.	O
)	O
</s>
<s>
The	O
study	O
also	O
showed	O
,	O
on	O
the	O
down-side	O
,	O
that	O
SSDs	B-Device
experience	O
significantly	O
higher	O
rates	O
of	O
uncorrectable	O
errors	O
(	O
which	O
cause	O
data	O
loss	O
)	O
than	O
do	O
HDDs	O
.	O
</s>
<s>
In	O
the	O
real	O
world	O
,	O
MLC-based	O
designs	O
–	O
believed	O
less	O
reliable	O
than	O
SLC	O
designs	O
–	O
are	O
often	O
as	O
reliable	O
as	O
SLC	O
.	O
</s>
<s>
(	O
The	O
findings	O
state	O
that	O
"	O
SLC	O
 [ is ] 	O
not	O
generally	O
more	O
reliable	O
than	O
MLC	B-Device
"	O
.	O
)	O
</s>
<s>
Device	O
age	O
,	O
measured	O
by	O
days	O
in	O
use	O
,	O
is	O
the	O
main	O
factor	O
in	O
SSD	B-Device
reliability	O
and	O
not	O
amount	O
of	O
data	O
read	O
or	O
written	O
,	O
which	O
are	O
measured	O
by	O
terabytes	O
written	O
or	O
drive	O
writes	O
per	O
day	O
.	O
</s>
<s>
RBER	O
is	O
not	O
a	O
good	O
predictor	O
of	O
other	O
errors	O
or	O
SSD	B-Device
failure	O
.	O
</s>
<s>
However	O
SSD	B-Device
UBER	O
rates	O
are	O
higher	O
than	O
those	O
for	O
HDDs	O
,	O
so	O
although	O
they	O
do	O
not	O
predict	O
failure	O
,	O
they	O
can	O
lead	O
to	O
data	O
loss	O
due	O
to	O
unreadable	O
blocks	O
being	O
more	O
common	O
on	O
SSDs	B-Device
than	O
HDDs	O
.	O
</s>
<s>
"	O
Bad	B-Device
blocks	I-Device
in	O
new	O
SSDs	B-Device
are	O
common	O
,	O
and	O
drives	O
with	O
a	O
large	O
number	O
of	O
bad	B-Device
blocks	I-Device
are	O
much	O
more	O
likely	O
to	O
lose	O
hundreds	O
of	O
other	O
blocks	O
,	O
most	O
likely	O
due	O
to	O
Flash	O
die	O
or	O
chip	O
failure	O
.	O
</s>
<s>
30	O
–	O
80%	O
of	O
SSDs	B-Device
develop	O
at	O
least	O
one	O
bad	B-Device
block	I-Device
and	O
2	O
–	O
7%	O
develop	O
at	O
least	O
one	O
bad	O
chip	O
in	O
the	O
first	O
four	O
years	O
of	O
deployment.	O
"	O
</s>
<s>
Most	O
SSDs	B-Device
develop	O
no	O
more	O
than	O
a	O
few	O
bad	B-Device
blocks	I-Device
,	O
perhaps	O
2	O
–	O
4	O
.	O
</s>
<s>
SSDs	B-Device
that	O
develop	O
many	O
bad	B-Device
blocks	I-Device
often	O
go	O
on	O
to	O
develop	O
far	O
more	O
(	O
perhaps	O
hundreds	O
)	O
,	O
and	O
may	O
be	O
prone	O
to	O
failure	O
.	O
</s>
<s>
However	O
most	O
drives	O
(	O
99%+	O
)	O
are	O
shipped	O
with	O
bad	B-Device
blocks	I-Device
from	O
manufacture	O
.	O
</s>
<s>
The	O
finding	O
overall	O
was	O
that	O
bad	B-Device
blocks	I-Device
are	O
common	O
and	O
30	O
–	O
80%	O
of	O
drives	O
will	O
develop	O
at	O
least	O
one	O
in	O
use	O
,	O
but	O
even	O
a	O
few	O
bad	B-Device
blocks	I-Device
(	O
2	O
–	O
4	O
)	O
is	O
a	O
predictor	O
of	O
up	O
to	O
hundreds	O
of	O
bad	B-Device
blocks	I-Device
at	O
a	O
later	O
time	O
.	O
</s>
<s>
The	O
bad	B-Device
block	I-Device
count	O
at	O
manufacture	O
correlates	O
with	O
later	O
development	O
of	O
further	O
bad	B-Device
blocks	I-Device
.	O
</s>
<s>
The	O
report	O
conclusion	O
added	O
that	O
SSDs	B-Device
tended	O
to	O
either	O
have	O
"	O
less	O
than	O
a	O
handful	O
"	O
of	O
bad	B-Device
blocks	I-Device
or	O
"	O
a	O
large	O
number	O
"	O
,	O
and	O
suggested	O
that	O
this	O
might	O
be	O
a	O
basis	O
for	O
predicting	O
eventual	O
failure	O
.	O
</s>
<s>
Around	O
2	O
–	O
7%	O
of	O
SSDs	B-Device
will	O
develop	O
bad	O
chips	O
in	O
their	O
first	O
four	O
years	O
of	O
use	O
.	O
</s>
<s>
96%	O
of	O
those	O
SSDs	B-Device
that	O
need	O
repair	O
(	O
warranty	O
servicing	O
)	O
,	O
need	O
repair	O
only	O
once	O
in	O
their	O
life	O
.	O
</s>
<s>
Solid-state	B-Device
drives	I-Device
have	O
set	O
new	O
challenges	O
for	O
data	B-Application
recovery	I-Application
companies	O
,	O
as	O
the	O
method	O
of	O
storing	O
data	O
is	O
non-linear	O
and	O
much	O
more	O
complex	O
than	O
that	O
of	O
hard	B-Device
disk	I-Device
drives	I-Device
.	O
</s>
<s>
Wear	B-Application
leveling	I-Application
also	O
means	O
that	O
the	O
physical	O
address	O
of	O
the	O
data	O
and	O
the	O
address	O
exposed	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
are	O
different	O
.	O
</s>
<s>
As	O
for	O
secure	O
deletion	O
of	O
data	O
,	O
ATA	B-Protocol
Secure	O
Erase	O
command	O
could	O
be	O
used	O
.	O
</s>
<s>
A	O
program	O
such	O
as	O
hdparm	B-Application
can	O
be	O
used	O
for	O
this	O
purpose	O
.	O
</s>
<s>
Due	O
to	O
their	O
generally	O
prohibitive	O
cost	O
versus	O
HDDs	O
at	O
the	O
time	O
,	O
until	O
2009	O
,	O
SSDs	B-Device
were	O
mainly	O
used	O
in	O
those	O
aspects	O
of	O
mission	B-Application
critical	I-Application
applications	O
where	O
the	O
speed	O
of	O
the	O
storage	B-General_Concept
system	I-General_Concept
needed	O
to	O
be	O
as	O
high	O
as	O
possible	O
.	O
</s>
<s>
Since	O
flash	B-Device
memory	I-Device
has	O
become	O
a	O
common	O
component	O
of	O
SSDs	B-Device
,	O
the	O
falling	O
prices	O
and	O
increased	O
densities	O
have	O
made	O
it	O
more	O
cost-effective	O
for	O
many	O
other	O
applications	O
.	O
</s>
<s>
For	O
instance	O
,	O
in	O
the	O
distributed	B-Architecture
computing	I-Architecture
environment	O
,	O
SSDs	B-Device
can	O
be	O
used	O
as	O
the	O
building	O
block	O
for	O
a	O
distributed	B-Operating_System
cache	I-Operating_System
layer	O
that	O
temporarily	O
absorbs	O
the	O
large	O
volume	O
of	O
user	O
requests	O
to	O
the	O
slower	O
HDD	B-Device
based	O
backend	O
storage	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
This	O
layer	O
provides	O
much	O
higher	O
bandwidth	O
and	O
lower	O
latency	B-General_Concept
than	O
the	O
storage	B-General_Concept
system	I-General_Concept
,	O
and	O
can	O
be	O
managed	O
in	O
a	O
number	O
of	O
forms	O
,	O
such	O
as	O
distributed	O
key-value	B-Data_Structure
database	I-Data_Structure
and	O
distributed	O
file	B-Application
system	I-Application
.	O
</s>
<s>
On	O
supercomputers	O
,	O
this	O
layer	O
is	O
typically	O
referred	O
to	O
as	O
burst	B-Operating_System
buffer	I-Operating_System
.	O
</s>
<s>
Flash-based	O
solid-state	B-Device
drives	I-Device
can	O
be	O
used	O
to	O
create	O
network	O
appliances	O
from	O
general-purpose	O
personal	B-Device
computer	I-Device
hardware	O
.	O
</s>
<s>
A	O
write	B-Device
protected	I-Device
flash	O
drive	O
containing	O
the	O
operating	B-General_Concept
system	I-General_Concept
and	O
application	O
software	O
can	O
substitute	O
for	O
larger	O
,	O
less	O
reliable	O
disk	O
drives	O
or	O
CD-ROMs	O
.	O
</s>
<s>
SSDs	B-Device
based	O
on	O
an	O
SD	B-Device
card	I-Device
with	O
a	O
live	O
SD	O
operating	B-General_Concept
system	I-General_Concept
are	O
easily	O
write-locked	O
.	O
</s>
<s>
Combined	O
with	O
a	O
cloud	B-Architecture
computing	I-Architecture
environment	O
or	O
other	O
writable	O
medium	O
,	O
to	O
maintain	O
persistence	B-Application
,	O
an	O
OS	B-General_Concept
booted	B-Operating_System
from	O
a	O
write-locked	O
SD	B-Device
card	I-Device
is	O
robust	O
,	O
rugged	O
,	O
reliable	O
,	O
and	O
impervious	O
to	O
permanent	O
corruption	O
.	O
</s>
<s>
If	O
the	O
running	O
OS	B-General_Concept
degrades	O
,	O
simply	O
turning	O
the	O
machine	O
off	O
and	O
then	O
on	O
returns	O
it	O
back	O
to	O
its	O
initial	O
uncorrupted	O
state	O
and	O
thus	O
is	O
particularly	O
solid	O
.	O
</s>
<s>
The	O
SD	B-Device
card	I-Device
installed	O
OS	B-General_Concept
does	O
not	O
require	O
removal	O
of	O
corrupted	O
components	O
since	O
it	O
was	O
write-locked	O
though	O
any	O
written	O
media	O
may	O
need	O
to	O
be	O
restored	O
.	O
</s>
<s>
In	O
2011	O
,	O
Intel	O
introduced	O
a	O
caching	B-General_Concept
mechanism	O
for	O
their	O
Z68	O
chipset	O
(	O
and	O
mobile	O
derivatives	O
)	O
called	O
Smart	B-Device
Response	I-Device
Technology	I-Device
,	O
which	O
allows	O
a	O
SATA	O
SSD	B-Device
to	O
be	O
used	O
as	O
a	O
cache	B-General_Concept
(	O
configurable	O
as	O
write-through	O
or	O
write-back	O
)	O
for	O
a	O
conventional	O
,	O
magnetic	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
Solid-state	B-Device
hybrid	I-Device
drives	I-Device
(	O
SSHDs	B-Device
)	O
are	O
based	O
on	O
the	O
same	O
principle	O
,	O
but	O
integrate	O
some	O
amount	O
of	O
flash	B-Device
memory	I-Device
on	O
board	O
of	O
a	O
conventional	O
drive	O
instead	O
of	O
using	O
a	O
separate	O
SSD	B-Device
.	O
</s>
<s>
The	O
flash	O
layer	O
in	O
these	O
drives	O
can	O
be	O
accessed	O
independently	O
from	O
the	O
magnetic	B-Architecture
storage	I-Architecture
by	O
the	O
host	O
using	O
ATA-8	O
commands	O
,	O
allowing	O
the	O
operating	B-General_Concept
system	I-General_Concept
to	O
manage	O
it	O
.	O
</s>
<s>
For	O
example	O
,	O
Microsoft	O
's	O
ReadyDrive	O
technology	O
explicitly	O
stores	O
portions	O
of	O
the	O
hibernation	O
file	O
in	O
the	O
cache	B-General_Concept
of	O
these	O
drives	O
when	O
the	O
system	O
hibernates	O
,	O
making	O
the	O
subsequent	O
resume	O
faster	O
.	O
</s>
<s>
Dual-drive	O
hybrid	O
systems	O
are	O
combining	O
the	O
usage	O
of	O
separate	O
SSD	B-Device
and	O
HDD	B-Device
devices	O
installed	O
in	O
the	O
same	O
computer	O
,	O
with	O
overall	O
performance	O
optimization	O
managed	O
by	O
the	O
computer	O
user	O
,	O
or	O
by	O
the	O
computer	O
's	O
operating	B-General_Concept
system	I-General_Concept
software	O
.	O
</s>
<s>
Examples	O
of	O
this	O
type	O
of	O
system	O
are	O
bcache	B-Application
and	O
dm-cache	B-Application
on	O
Linux	B-Application
,	O
and	O
Apple	O
's	O
Fusion	B-Device
Drive	I-Device
.	O
</s>
<s>
Typically	O
the	O
same	O
file	B-Application
systems	I-Application
used	O
on	O
hard	B-Device
disk	I-Device
drives	I-Device
can	O
also	O
be	O
used	O
on	O
solid	B-Device
state	I-Device
drives	I-Device
.	O
</s>
<s>
It	O
is	O
usually	O
expected	O
for	O
the	O
file	B-Application
system	I-Application
to	O
support	O
the	O
TRIM	O
command	O
which	O
helps	O
the	O
SSD	B-Device
to	O
recycle	O
discarded	O
data	O
(	O
support	O
for	O
TRIM	O
arrived	O
some	O
years	O
after	O
SSDs	B-Device
themselves	O
but	O
is	O
now	O
nearly	O
universal	O
)	O
.	O
</s>
<s>
This	O
means	O
that	O
the	O
file	B-Application
system	I-Application
does	O
not	O
need	O
to	O
manage	O
wear	B-Application
leveling	I-Application
or	O
other	O
flash	B-Device
memory	I-Device
characteristics	O
,	O
as	O
they	O
are	O
handled	O
internally	O
by	O
the	O
SSD	B-Device
.	O
</s>
<s>
Some	O
log-structured	B-Application
file	I-Application
systems	I-Application
(	O
e.g.	O
</s>
<s>
F2FS	B-Application
,	O
JFFS2	B-Application
)	O
help	O
to	O
reduce	O
write	B-Error_Name
amplification	I-Error_Name
on	O
SSDs	B-Device
,	O
especially	O
in	O
situations	O
where	O
only	O
very	O
small	O
amounts	O
of	O
data	O
are	O
changed	O
,	O
such	O
as	O
when	O
updating	O
file-system	B-Application
metadata	O
.	O
</s>
<s>
While	O
not	O
a	O
native	O
feature	O
of	O
file	B-Application
systems	I-Application
,	O
operating	B-General_Concept
systems	I-General_Concept
should	O
also	O
aim	O
to	O
align	O
partitions	O
correctly	O
,	O
which	O
avoids	O
excessive	O
read-modify-write	B-Operating_System
cycles	O
.	O
</s>
<s>
A	O
typical	O
practice	O
for	O
personal	B-Device
computers	I-Device
is	O
to	O
have	O
each	O
partition	O
aligned	O
to	O
start	O
at	O
a	O
1MiB	O
(=	O
1,048,576	O
bytes	O
)	O
mark	O
,	O
which	O
covers	O
all	O
common	O
SSD	B-Device
page	O
and	O
block	O
size	O
scenarios	O
,	O
as	O
it	O
is	O
divisible	O
by	O
all	O
commonly	O
used	O
sizes	O
-	O
1MiB	O
,	O
512KiB	O
,	O
128KiB	O
,	O
4KiB	O
,	O
and	O
512B	O
.	O
</s>
<s>
Modern	O
operating	B-General_Concept
system	I-General_Concept
installation	O
software	O
and	O
disk	O
tools	O
handle	O
this	O
automatically	O
.	O
</s>
<s>
Initial	O
support	O
for	O
the	O
TRIM	O
command	O
has	O
been	O
added	O
to	O
version	O
2.6.28	O
of	O
the	O
Linux	B-Application
kernel	O
mainline	O
.	O
</s>
<s>
The	O
ext4	B-Application
,	O
Btrfs	B-Operating_System
,	O
XFS	B-Application
,	O
JFS	B-Application
,	O
and	O
F2FS	B-Application
file	B-Application
systems	I-Application
include	O
support	O
for	O
the	O
discard	O
(	O
TRIM	O
or	O
UNMAP	O
)	O
function	O
.	O
</s>
<s>
Kernel	O
support	O
for	O
the	O
TRIM	O
operation	O
was	O
introduced	O
in	O
version	O
2.6.33	O
of	O
the	O
Linux	B-Application
kernel	O
mainline	O
,	O
released	O
on	O
24	O
February	O
2010	O
.	O
</s>
<s>
To	O
make	O
use	O
of	O
it	O
,	O
a	O
file	B-Application
system	I-Application
must	O
be	O
mounted	O
using	O
the	O
discard	O
parameter	O
.	O
</s>
<s>
Linux	B-Application
swap	B-Architecture
partitions	O
are	O
by	O
default	O
performing	O
discard	O
operations	O
when	O
the	O
underlying	O
drive	O
supports	O
TRIM	O
,	O
with	O
the	O
possibility	O
to	O
turn	O
them	O
off	O
,	O
or	O
to	O
select	O
between	O
one-time	O
or	O
continuous	O
discard	O
operations	O
.	O
</s>
<s>
Support	O
for	O
queued	O
TRIM	O
,	O
which	O
is	O
a	O
SATA	O
3.1	O
feature	O
that	O
results	O
in	O
TRIM	O
commands	O
not	O
disrupting	O
the	O
command	O
queues	O
,	O
was	O
introduced	O
in	O
Linux	B-Application
kernel	O
3.12	O
,	O
released	O
on	O
November	O
2	O
,	O
2013	O
.	O
</s>
<s>
An	O
alternative	O
to	O
the	O
kernel-level	O
TRIM	O
operation	O
is	O
to	O
use	O
a	O
user-space	O
utility	O
called	O
that	O
goes	O
through	O
all	O
of	O
the	O
unused	O
blocks	O
in	O
a	O
filesystem	B-Application
and	O
dispatches	O
TRIM	O
commands	O
for	O
those	O
areas	O
.	O
</s>
<s>
utility	O
is	O
usually	O
run	O
by	O
cron	B-General_Concept
as	O
a	O
scheduled	O
task	O
.	O
</s>
<s>
,	O
it	O
is	O
used	O
by	O
the	O
Ubuntu	B-Operating_System
Linux	I-Operating_System
distribution	I-Operating_System
,	O
in	O
which	O
it	O
is	O
enabled	O
only	O
for	O
Intel	O
and	O
Samsung	O
solid-state	B-Device
drives	I-Device
for	O
reliability	O
reasons	O
;	O
vendor	O
check	O
can	O
be	O
disabled	O
by	O
editing	O
file	O
using	O
instructions	O
contained	O
within	O
the	O
file	O
itself	O
.	O
</s>
<s>
Since	O
2010	O
,	O
standard	O
Linux	B-Application
drive	O
utilities	O
have	O
taken	O
care	O
of	O
appropriate	O
partition	O
alignment	O
by	O
default	O
.	O
</s>
<s>
During	O
installation	O
,	O
Linux	B-Application
distributions	I-Application
usually	O
do	O
not	O
configure	O
the	O
installed	O
system	O
to	O
use	O
TRIM	O
and	O
thus	O
the	O
/etc/fstab	B-Protocol
file	O
requires	O
manual	O
modifications	O
.	O
</s>
<s>
This	O
is	O
because	O
of	O
the	O
notion	O
that	O
the	O
current	O
Linux	B-Application
TRIM	O
command	O
implementation	O
might	O
not	O
be	O
optimal	O
.	O
</s>
<s>
Linux	B-Application
sends	O
an	O
individual	O
TRIM	O
command	O
to	O
each	O
sector	O
,	O
instead	O
of	O
a	O
vectorized	O
list	O
defining	O
a	O
TRIM	O
range	O
as	O
recommended	O
by	O
the	O
TRIM	O
specification	O
.	O
</s>
<s>
For	O
performance	O
reasons	O
,	O
it	O
is	O
recommended	O
to	O
switch	O
the	O
I/O	O
scheduler	O
from	O
the	O
default	O
CFQ	B-Application
(	O
Completely	B-Application
Fair	I-Application
Queuing	I-Application
)	O
to	O
NOOP	O
or	O
Deadline	O
.	O
</s>
<s>
CFQ	B-Application
was	O
designed	O
for	O
traditional	O
magnetic	B-Architecture
media	I-Architecture
and	O
seek	O
optimization	O
,	O
thus	O
many	O
of	O
those	O
I/O	O
scheduling	O
efforts	O
are	O
wasted	O
when	O
used	O
with	O
SSDs	B-Device
.	O
</s>
<s>
As	O
part	O
of	O
their	O
designs	O
,	O
SSDs	B-Device
offer	O
much	O
bigger	O
levels	O
of	O
parallelism	O
for	O
I/O	O
operations	O
,	O
so	O
it	O
is	O
preferable	O
to	O
leave	O
scheduling	O
decisions	O
to	O
their	O
internal	O
logic	O
especially	O
for	O
high-end	O
SSDs	B-Device
.	O
</s>
<s>
A	O
scalable	O
block	O
layer	O
for	O
high-performance	O
SSD	B-Device
storage	O
,	O
known	O
as	O
blk-multiqueue	O
or	O
blk-mq	O
and	O
developed	O
primarily	O
by	O
Fusion-io	O
engineers	O
,	O
was	O
merged	O
into	O
the	O
Linux	B-Application
kernel	O
mainline	O
in	O
kernel	O
version	O
3.13	O
,	O
released	O
on	O
19	O
January	O
2014	O
.	O
</s>
<s>
This	O
leverages	O
the	O
performance	O
offered	O
by	O
SSDs	B-Device
and	O
NVMe	B-Application
,	O
by	O
allowing	O
much	O
higher	O
I/O	O
submission	O
rates	O
.	O
</s>
<s>
With	O
this	O
new	O
design	O
of	O
the	O
Linux	B-Application
kernel	O
block	O
layer	O
,	O
internal	O
queues	O
are	O
split	O
into	O
two	O
levels	O
(	O
per-CPU	O
and	O
hardware-submission	O
queues	O
)	O
,	O
thus	O
removing	O
bottlenecks	O
and	O
allowing	O
much	O
higher	O
levels	O
of	O
I/O	O
parallelization	O
.	O
</s>
<s>
As	O
of	O
version	O
4.0	O
of	O
the	O
Linux	B-Application
kernel	O
,	O
released	O
on	O
12	O
April	O
2015	O
,	O
VirtIO	B-Application
block	O
driver	O
,	O
the	O
SCSI	B-Architecture
layer	O
(	O
which	O
is	O
used	O
by	O
Serial	O
ATA	B-Protocol
drivers	O
)	O
,	O
device	B-Application
mapper	I-Application
framework	O
,	O
loop	B-Application
device	I-Application
driver	O
,	O
unsorted	O
block	O
images	O
(	O
UBI	O
)	O
driver	O
(	O
which	O
implements	O
erase	O
block	O
management	O
layer	O
for	O
flash	B-Device
memory	I-Device
devices	O
)	O
and	O
RBD	O
driver	O
(	O
which	O
exports	O
Ceph	B-Operating_System
RADOS	O
objects	O
as	O
block	O
devices	O
)	O
have	O
been	O
modified	O
to	O
actually	O
use	O
this	O
new	O
interface	O
;	O
other	O
drivers	O
will	O
be	O
ported	O
in	O
the	O
following	O
releases	O
.	O
</s>
<s>
Versions	O
since	O
Mac	O
OS	B-General_Concept
X	O
10.6.8	O
(	O
Snow	O
Leopard	O
)	O
support	O
TRIM	O
but	O
only	O
when	O
used	O
with	O
an	O
Apple-purchased	O
SSD	B-Device
.	O
</s>
<s>
Versions	O
since	O
OS	B-General_Concept
X	O
10.10.4	O
(	O
Yosemite	O
)	O
include	O
sudo	O
trimforce	O
enable	O
as	O
a	O
Terminal	O
command	O
that	O
enables	O
TRIM	O
on	O
non-Apple	O
SSDs	B-Device
.	O
</s>
<s>
There	O
is	O
also	O
a	O
technique	O
to	O
enable	O
TRIM	O
in	O
versions	O
earlier	O
than	O
Mac	O
OS	B-General_Concept
X	O
10.6.8	O
,	O
although	O
it	O
remains	O
uncertain	O
whether	O
TRIM	O
is	O
actually	O
utilized	O
properly	O
in	O
those	O
cases	O
.	O
</s>
<s>
Prior	O
to	O
version	O
7	O
,	O
Microsoft	O
Windows	O
did	O
not	O
take	O
any	O
specific	O
measures	O
to	O
support	O
solid	B-Device
state	I-Device
drives	I-Device
.	O
</s>
<s>
From	O
Windows7	O
,	O
the	O
standard	O
NTFS	B-Application
file	I-Application
system	I-Application
provides	O
support	O
for	O
the	O
TRIM	O
command	O
.	O
</s>
<s>
(	O
Other	O
file	B-Application
systems	I-Application
on	O
Windows7	O
do	O
not	O
support	O
TRIM	O
.	O
)	O
</s>
<s>
By	O
default	O
,	O
Windows7	O
and	O
newer	O
versions	O
execute	O
TRIM	O
commands	O
automatically	O
if	O
the	O
device	O
is	O
detected	O
to	O
be	O
a	O
solid-state	B-Device
drive	I-Device
.	O
</s>
<s>
However	O
,	O
because	O
TRIM	O
irreversibly	O
resets	O
all	O
freed	O
space	O
,	O
it	O
may	O
be	O
desirable	O
to	O
disable	O
support	O
where	O
enabling	O
data	B-Application
recovery	I-Application
is	O
preferred	O
over	O
wear	B-Application
leveling	I-Application
.	O
</s>
<s>
To	O
change	O
the	O
behavior	O
,	O
in	O
the	O
Registry	B-Protocol
key	I-Protocol
the	O
value	O
can	O
be	O
set	O
to	O
.	O
</s>
<s>
The	O
TRIM	O
operation	O
is	O
fully	O
integrated	O
with	O
partition	O
-	O
and	O
volume-level	O
commands	O
such	O
as	O
format	O
and	O
delete	O
,	O
with	O
file-system	B-Application
commands	O
relating	O
to	O
truncate	O
and	O
compression	O
,	O
and	O
with	O
the	O
System	O
Restore	O
(	O
also	O
known	O
as	O
Volume	O
Snapshot	O
)	O
feature	O
.	O
</s>
<s>
Windows	B-Application
Vista	I-Application
generally	O
expects	O
hard	B-Device
disk	I-Device
drives	I-Device
rather	O
than	O
SSDs	B-Device
.	O
</s>
<s>
Windows	B-Application
Vista	I-Application
includes	O
ReadyBoost	O
to	O
exploit	O
characteristics	O
of	O
USB-connected	O
flash	O
devices	O
,	O
but	O
for	O
SSDs	B-Device
it	O
only	O
improves	O
the	O
default	O
partition	O
alignment	O
to	O
prevent	O
read-modify-write	B-Operating_System
operations	O
that	O
reduce	O
the	O
speed	O
of	O
SSDs	B-Device
.	O
</s>
<s>
Most	O
SSDs	B-Device
are	O
typically	O
split	O
into	O
4KiB	O
sectors	O
,	O
while	O
most	O
systems	O
are	O
based	O
on	O
512byte	O
sectors	O
with	O
their	O
default	O
partition	O
setups	O
unaligned	O
to	O
the	O
4KiB	O
boundaries	O
.	O
</s>
<s>
Defragmentation	B-Application
should	O
be	O
disabled	O
on	O
solid-state	B-Device
drives	I-Device
because	O
the	O
location	O
of	O
the	O
file	O
components	O
on	O
an	O
SSD	B-Device
does	O
not	O
significantly	O
impact	O
its	O
performance	O
,	O
but	O
moving	O
the	O
files	O
to	O
make	O
them	O
contiguous	B-Architecture
using	O
the	O
Windows	O
Defrag	B-Application
routine	O
will	O
cause	O
unnecessary	O
write	O
wear	O
on	O
the	O
limited	O
number	O
of	O
P/E	O
cycles	O
on	O
the	O
SSD	B-Device
.	O
</s>
<s>
The	O
Superfetch	O
feature	O
will	O
not	O
materially	O
improve	O
performance	O
and	O
causes	O
additional	O
overhead	O
in	O
the	O
system	O
and	O
SSD	B-Device
.	O
</s>
<s>
Windows	B-Application
Vista	I-Application
does	O
not	O
send	O
the	O
TRIM	O
command	O
to	O
solid-state	B-Device
drives	I-Device
,	O
but	O
some	O
third-party	O
utilities	O
such	O
as	O
SSD	B-Device
Doctor	O
will	O
periodically	O
scan	O
the	O
drive	O
and	O
TRIM	O
the	O
appropriate	O
entries	O
.	O
</s>
<s>
Windows7	O
and	O
later	O
versions	O
have	O
native	O
support	O
for	O
SSDs	B-Device
.	O
</s>
<s>
The	O
operating	B-General_Concept
system	I-General_Concept
detects	O
the	O
presence	O
of	O
an	O
SSD	B-Device
and	O
optimizes	O
operation	O
accordingly	O
.	O
</s>
<s>
For	O
SSD	B-Device
devices	O
,	O
Windows	O
7	O
disables	O
ReadyBoost	O
and	O
automatic	O
defragmentation	B-Application
.	O
</s>
<s>
Despite	O
the	O
initial	O
statement	O
by	O
Steven	O
Sinofsky	O
before	O
the	O
release	O
of	O
Windows	O
7	O
,	O
however	O
,	O
defragmentation	B-Application
is	O
not	O
disabled	O
,	O
even	O
though	O
its	O
behavior	O
on	O
SSDs	B-Device
differs	O
.	O
</s>
<s>
One	O
reason	O
is	O
the	O
low	O
performance	O
of	O
Volume	O
Shadow	O
Copy	O
Service	O
on	O
fragmented	O
SSDs	B-Device
.	O
</s>
<s>
Windows	O
7	O
also	O
includes	O
support	O
for	O
the	O
TRIM	O
command	O
to	O
reduce	O
garbage	O
collection	O
for	O
data	O
that	O
the	O
operating	B-General_Concept
system	I-General_Concept
has	O
already	O
determined	O
is	O
no	O
longer	O
valid	O
.	O
</s>
<s>
Without	O
support	O
for	O
TRIM	O
,	O
the	O
SSD	B-Device
would	O
be	O
unaware	O
of	O
this	O
data	O
being	O
invalid	O
and	O
would	O
unnecessarily	O
continue	O
to	O
rewrite	O
it	O
during	O
garbage	O
collection	O
causing	O
further	O
wear	O
on	O
the	O
SSD	B-Device
.	O
</s>
<s>
It	O
is	O
beneficial	O
to	O
make	O
some	O
changes	O
that	O
prevent	O
SSDs	B-Device
from	O
being	O
treated	O
more	O
like	O
HDDs	O
,	O
for	O
example	O
cancelling	O
defragmentation	B-Application
,	O
not	O
filling	O
them	O
to	O
more	O
than	O
about	O
75%	O
of	O
capacity	O
,	O
not	O
storing	O
frequently	O
written-to	O
files	O
such	O
as	O
log	O
and	O
temporary	O
files	O
on	O
them	O
if	O
a	O
hard	B-Device
drive	I-Device
is	O
available	O
,	O
and	O
enabling	O
the	O
TRIM	O
process	O
.	O
</s>
<s>
Windows	O
8.1	O
and	O
later	O
Windows	O
systems	O
also	O
support	O
automatic	O
TRIM	O
for	O
PCI	O
Express	O
SSDs	B-Device
based	O
on	O
NVMe	B-Application
.	O
</s>
<s>
For	O
Windows	O
7	O
,	O
the	O
KB2990941	O
update	O
is	O
required	O
for	O
this	O
functionality	O
and	O
needs	O
to	O
be	O
integrated	O
into	O
Windows	O
Setup	O
using	O
DISM	O
if	O
Windows	O
7	O
has	O
to	O
be	O
installed	O
on	O
the	O
NVMe	B-Application
SSD	B-Device
.	O
</s>
<s>
Windows	O
8/8.1	O
also	O
support	O
the	O
SCSI	B-Architecture
unmap	O
command	O
for	O
USB-attached	O
SSDs	B-Device
or	O
SATA-to-USB	O
enclosures	O
.	O
</s>
<s>
SCSI	B-Architecture
Unmap	O
is	O
a	O
full	O
analog	O
of	O
the	O
SATA	O
TRIM	O
command	O
.	O
</s>
<s>
It	O
is	O
also	O
supported	O
over	O
USB	B-Protocol
Attached	O
SCSI	B-Architecture
Protocol	O
(	O
UASP	O
)	O
.	O
</s>
<s>
The	O
graphical	O
Windows	O
Disk	B-Application
Defragmenter	I-Application
in	O
Windows	O
8.1	O
also	O
recognizes	O
SSDs	B-Device
distinctly	O
from	O
hard	B-Device
disk	I-Device
drives	I-Device
in	O
a	O
separate	O
Media	O
Type	O
column	O
.	O
</s>
<s>
While	O
Windows	O
7	O
supported	O
automatic	O
TRIM	O
for	O
internal	O
SATA	O
SSDs	B-Device
,	O
Windows	O
8.1	O
and	O
Windows	O
10	O
support	O
manual	O
TRIM	O
(	O
via	O
an	O
"	O
Optimize	O
"	O
function	O
in	O
Disk	B-Application
Defragmenter	I-Application
)	O
as	O
well	O
as	O
automatic	O
TRIM	O
for	O
SATA	O
,	O
NVMe	B-Application
and	O
USB-attached	O
SSDs	B-Device
.	O
</s>
<s>
Disk	B-Application
Defragmenter	I-Application
in	O
Windows	O
10	O
and	O
11	O
may	O
execute	O
TRIM	O
to	O
optimize	O
an	O
SSD	B-Device
.	O
</s>
<s>
Solaris	B-Application
as	O
of	O
version	O
10	O
Update	O
6	O
(	O
released	O
in	O
October	O
2008	O
)	O
,	O
and	O
recent	O
versions	O
of	O
OpenSolaris	B-Operating_System
,	O
Solaris	B-Application
Express	I-Application
Community	O
Edition	O
,	O
Illumos	B-Application
,	O
Linux	B-Application
with	O
ZFS	B-Application
on	O
Linux	B-Application
,	O
and	O
FreeBSD	B-Operating_System
all	O
can	O
use	O
SSDs	B-Device
as	O
a	O
performance	O
booster	O
for	O
ZFS	B-Application
.	O
</s>
<s>
A	O
low-latency	O
SSD	B-Device
can	O
be	O
used	O
for	O
the	O
ZFS	B-Application
Intent	O
Log	O
(	O
ZIL	O
)	O
,	O
where	O
it	O
is	O
named	O
the	O
SLOG	O
.	O
</s>
<s>
An	O
SSD	B-Device
(	O
not	O
necessarily	O
with	O
a	O
low-latency	O
)	O
may	O
also	O
be	O
used	O
for	O
the	O
level	O
2	O
Adaptive	B-General_Concept
Replacement	I-General_Concept
Cache	I-General_Concept
(	O
L2ARC	B-Application
)	O
,	O
which	O
is	O
used	O
to	O
cache	B-General_Concept
data	O
for	O
reading	O
.	O
</s>
<s>
ZFS	B-Application
for	O
FreeBSD	B-Operating_System
introduced	O
support	O
for	O
TRIM	O
on	O
September	O
23	O
,	O
2012	O
.	O
</s>
<s>
Also	O
the	O
Unix	B-Operating_System
File	I-Operating_System
System	I-Operating_System
(	O
UFS	O
)	O
supports	O
the	O
TRIM	O
command	O
.	O
</s>
<s>
According	O
to	O
Microsoft	O
's	O
former	O
Windows	O
division	O
president	O
Steven	O
Sinofsky	O
,	O
"	O
there	O
are	O
few	O
files	O
better	O
than	O
the	O
pagefile	B-Architecture
to	O
place	O
on	O
an	O
SSD	B-Device
"	O
.	O
</s>
<s>
According	O
to	O
collected	O
telemetry	O
data	O
,	O
Microsoft	O
had	O
found	O
the	O
pagefile.sys	O
to	O
be	O
an	O
ideal	O
match	O
for	O
SSD	B-Device
storage	O
.	O
</s>
<s>
Linux	B-Application
swap	B-Architecture
partitions	O
are	O
by	O
default	O
performing	O
TRIM	O
operations	O
when	O
the	O
underlying	O
block	O
device	O
supports	O
TRIM	O
,	O
with	O
the	O
possibility	O
to	O
turn	O
them	O
off	O
,	O
or	O
to	O
select	O
between	O
one-time	O
or	O
continuous	O
TRIM	O
operations	O
.	O
</s>
<s>
If	O
an	O
operating	B-General_Concept
system	I-General_Concept
does	O
not	O
support	O
using	O
TRIM	O
on	O
discrete	O
swap	B-Architecture
partitions	O
,	O
it	O
might	O
be	O
possible	O
to	O
use	O
swap	B-Architecture
files	O
inside	O
an	O
ordinary	O
file	B-Application
system	I-Application
instead	O
.	O
</s>
<s>
For	O
example	O
,	O
OSX	O
does	O
not	O
support	O
swap	B-Architecture
partitions	O
;	O
it	O
only	O
swaps	O
to	O
files	O
within	O
a	O
file	B-Application
system	I-Application
,	O
so	O
it	O
can	O
use	O
TRIM	O
when	O
,	O
for	O
example	O
,	O
swap	B-Architecture
files	O
are	O
deleted	O
.	O
</s>
<s>
DragonFly	B-Application
BSD	I-Application
allows	O
SSD-configured	O
swap	B-Architecture
to	O
also	O
be	O
used	O
as	O
file-system	B-Application
cache	B-General_Concept
.	O
</s>
<s>
The	O
bcache	B-Application
,	O
dm-cache	B-Application
,	O
and	O
Flashcache	B-Application
projects	O
provide	O
a	O
similar	O
concept	O
for	O
the	O
Linux	B-Application
kernel	O
.	O
</s>
<s>
The	O
following	O
are	O
noted	O
standardization	O
organizations	O
and	O
bodies	O
that	O
work	O
to	O
create	O
standards	O
for	O
solid-state	B-Device
drives	I-Device
(	O
and	O
other	O
computer	B-General_Concept
storage	I-General_Concept
devices	I-General_Concept
)	O
.	O
</s>
<s>
The	O
table	O
below	O
also	O
includes	O
organizations	O
which	O
promote	O
the	O
use	O
of	O
solid-state	B-Device
drives	I-Device
.	O
</s>
<s>
Solid-state	B-Device
drive	I-Device
technology	O
has	O
been	O
marketed	O
to	O
the	O
military	O
and	O
niche	O
industrial	O
markets	O
since	O
the	O
mid-1990s	O
.	O
</s>
<s>
Along	O
with	O
the	O
emerging	O
enterprise	O
market	O
,	O
SSDs	B-Device
have	O
been	O
appearing	O
in	O
ultra-mobile	O
PCs	B-Device
and	O
a	O
few	O
lightweight	O
laptop	O
systems	O
,	O
adding	O
significantly	O
to	O
the	O
price	O
of	O
the	O
laptop	O
,	O
depending	O
on	O
the	O
capacity	O
,	O
form	O
factor	O
and	O
transfer	O
speeds	O
.	O
</s>
<s>
For	O
low-end	O
applications	O
,	O
a	O
USB	B-Protocol
flash	O
drive	O
may	O
be	O
obtainable	O
for	O
anywhere	O
from	O
$10	O
to	O
$100	O
or	O
so	O
,	O
depending	O
on	O
capacity	O
and	O
speed	O
;	O
alternatively	O
,	O
a	O
CompactFlash	B-Device
card	I-Device
may	O
be	O
paired	O
with	O
a	O
CF-to-IDE	O
or	O
CF-to-SATA	O
converter	O
at	O
a	O
similar	O
cost	O
.	O
</s>
<s>
Either	O
of	O
these	O
requires	O
that	O
write-cycle	O
endurance	O
issues	O
be	O
managed	O
,	O
either	O
by	O
refraining	O
from	O
storing	O
frequently	O
written	O
files	O
on	O
the	O
drive	O
or	O
by	O
using	O
a	O
flash	B-Application
file	I-Application
system	I-Application
.	O
</s>
<s>
Standard	O
CompactFlash	B-Device
cards	I-Device
usually	O
have	O
write	O
speeds	O
of	O
7	O
to	O
15MB/s	O
while	O
the	O
more	O
expensive	O
upmarket	O
cards	O
claim	O
speeds	O
of	O
up	O
to	O
60MB/s	O
.	O
</s>
<s>
The	O
first	O
flash-memory	O
SSD	B-Device
based	O
PC	O
to	O
become	O
available	O
was	O
the	O
Sony	O
Vaio	O
UX90	O
,	O
announced	O
for	O
pre-order	O
on	O
27	O
June	O
2006	O
and	O
began	O
shipping	O
in	O
Japan	O
on	O
3	O
July	O
2006	O
with	O
a	O
16	O
GB	O
flash	B-Device
memory	I-Device
hard	B-Device
drive	I-Device
.	O
</s>
<s>
In	O
late	O
September	O
2006	O
Sony	O
upgraded	O
the	O
SSD	B-Device
in	O
the	O
Vaio	O
UX90	O
to	O
32	O
GB	O
.	O
</s>
<s>
One	O
of	O
the	O
first	O
mainstream	O
releases	O
of	O
SSD	B-Device
was	O
the	O
XO	B-Application
Laptop	I-Application
,	O
built	O
as	O
part	O
of	O
the	O
One	O
Laptop	O
Per	O
Child	O
project	O
.	O
</s>
<s>
Dell	O
began	O
shipping	O
ultra-portable	O
laptops	O
with	O
SanDisk	O
SSDs	B-Device
on	O
April	O
26	O
,	O
2007	O
.	O
</s>
<s>
Asus	O
released	O
the	O
Eee	B-Device
PC	I-Device
netbook	B-Device
on	O
October	O
16	O
,	O
2007	O
,	O
with	O
2	O
,	O
4	O
or	O
8	O
gigabytes	O
of	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
In	O
2008	O
two	O
manufacturers	O
released	O
the	O
ultrathin	O
laptops	O
with	O
SSD	B-Device
options	O
instead	O
of	O
uncommon	O
1.8	O
"	O
HDD	B-Device
:	O
this	O
was	O
a	O
MacBook	B-Device
Air	I-Device
,	O
released	O
by	O
the	O
Apple	O
in	O
a	O
January	O
31	O
,	O
with	O
an	O
optional	O
64GB	O
SSD	B-Device
(	O
The	O
Apple	O
Store	O
cost	O
was	O
$999	O
more	O
for	O
this	O
option	O
,	O
as	O
compared	O
with	O
that	O
of	O
an	O
80GB	O
4200RPM	O
HDD	B-Device
)	O
,	O
And	O
the	O
Lenovo	B-Operating_System
ThinkPad	I-Operating_System
X300	O
with	O
a	O
similar	O
64gigabyte	O
SSD	B-Device
,	O
announced	O
in	O
February	O
2008	O
and	O
upgraded	O
to	O
128GB	O
SSD	B-Device
option	O
on	O
August	O
26	O
,	O
2008	O
,	O
with	O
release	O
of	O
ThinkPad	B-Operating_System
X301	O
model	O
(	O
an	O
upgrade	O
which	O
added	O
approximately	O
$200	O
US	O
)	O
.	O
</s>
<s>
In	O
2008	O
,	O
low-end	O
netbooks	B-Device
appeared	O
with	O
SSDs	B-Device
.	O
</s>
<s>
In	O
2009	O
,	O
SSDs	B-Device
began	O
to	O
appear	O
in	O
laptops	O
.	O
</s>
<s>
On	O
January	O
14	O
,	O
2008	O
,	O
EMC	O
Corporation	O
(	O
EMC	O
)	O
became	O
the	O
first	O
enterprise	O
storage	O
vendor	O
to	O
ship	O
flash-based	O
SSDs	B-Device
into	O
its	O
product	O
portfolio	O
when	O
it	O
announced	O
it	O
had	O
selected	O
STEC	O
,	O
Inc.	O
'	O
s	O
Zeus-IOPS	O
SSDs	B-Device
for	O
its	O
Symmetrix	O
DMX	O
systems	O
.	O
</s>
<s>
In	O
2008	O
,	O
Sun	O
released	O
the	O
Sun	O
Storage	O
7000	O
Unified	O
Storage	B-General_Concept
Systems	I-General_Concept
(	O
codenamed	O
Amber	O
Road	O
)	O
,	O
which	O
use	O
both	O
solid	B-Device
state	I-Device
drives	I-Device
and	O
conventional	O
hard	B-Device
drives	I-Device
to	O
take	O
advantage	O
of	O
the	O
speed	O
offered	O
by	O
SSDs	B-Device
and	O
the	O
economy	O
and	O
capacity	O
offered	O
by	O
conventional	O
HDDs	O
.	O
</s>
<s>
Dell	O
began	O
to	O
offer	O
optional	O
256GB	O
solid	B-Device
state	I-Device
drives	I-Device
on	O
select	O
notebook	O
models	O
in	O
January	O
2009	O
.	O
</s>
<s>
In	O
May	O
2009	O
,	O
Toshiba	O
launched	O
a	O
laptop	O
with	O
a	O
512GB	O
SSD	B-Device
.	O
</s>
<s>
Since	O
October	O
2010	O
,	O
Apple	O
's	O
MacBook	B-Device
Air	I-Device
line	O
has	O
used	O
a	O
solid	B-Device
state	I-Device
drive	I-Device
as	O
standard	O
.	O
</s>
<s>
In	O
December	O
2010	O
,	O
OCZ	O
RevoDrive	O
X2	O
PCIe	O
SSD	B-Device
was	O
available	O
in	O
100GB	O
to	O
960GB	O
capacities	O
delivering	O
speeds	O
over	O
740MB/s	O
sequential	O
speeds	O
and	O
random	O
small	O
file	O
writes	O
up	O
to	O
120,000	O
IOPS	O
.	O
</s>
<s>
In	O
November	O
2010	O
,	O
Fusion-io	O
released	O
its	O
highest	O
performing	O
SSD	B-Device
drive	I-Device
named	O
ioDrive	O
Octal	O
utilising	O
PCI-Express	O
x16	O
Gen	O
2.0	O
interface	O
with	O
storage	O
space	O
of	O
5.12TB	O
,	O
read	O
speed	O
of	O
6.0GB/s	O
,	O
write	O
speed	O
of	O
4.4GB/s	O
and	O
a	O
low	O
latency	B-General_Concept
of	O
30microseconds	O
.	O
</s>
<s>
In	O
2011	O
,	O
computers	O
based	O
on	O
Intel	O
's	O
Ultrabook	B-Device
specifications	O
became	O
available	O
.	O
</s>
<s>
These	O
specifications	O
dictate	O
that	O
Ultrabooks	B-Device
use	O
an	O
SSD	B-Device
.	O
</s>
<s>
These	O
are	O
consumer-level	O
devices	O
(	O
unlike	O
many	O
previous	O
flash	O
offerings	O
aimed	O
at	O
enterprise	O
users	O
)	O
,	O
and	O
represent	O
the	O
first	O
widely	O
available	O
consumer	O
computers	O
using	O
SSDs	B-Device
aside	O
from	O
the	O
MacBook	B-Device
Air	I-Device
.	O
</s>
<s>
At	O
CES	O
2012	O
,	O
OCZ	O
Technology	O
demonstrated	O
the	O
R4	O
CloudServ	O
PCIe	O
SSDs	B-Device
capable	O
of	O
reaching	O
transfer	O
speeds	O
of	O
6.5GB/s	O
and	O
1.4million	O
IOPS	O
.	O
</s>
<s>
In	O
December	O
2013	O
,	O
Samsung	O
introduced	O
and	O
launched	O
the	O
industry	O
's	O
first	O
1TB	O
mSATA	O
SSD	B-Device
.	O
</s>
<s>
In	O
August	O
2015	O
,	O
Samsung	O
announced	O
a	O
16TB	O
SSD	B-Device
,	O
at	O
the	O
time	O
the	O
world	O
's	O
highest-capacity	O
single	O
storage	O
device	O
of	O
any	O
type	O
.	O
</s>
<s>
While	O
a	O
number	O
of	O
companies	O
offer	O
SSD	B-Device
devices	O
only	O
five	O
of	O
the	O
companies	O
that	O
offer	O
them	O
actually	O
manufacture	O
the	O
NAND	O
flash	O
devices	O
that	O
are	O
the	O
storage	O
element	O
in	O
SSDs	B-Device
.	O
</s>
<s>
SSD	B-Device
technology	O
has	O
been	O
developing	O
rapidly	O
.	O
</s>
<s>
Most	O
of	O
the	O
performance	O
measurements	O
used	O
on	O
disk	O
drives	O
with	O
rotating	O
media	O
are	O
also	O
used	O
on	O
SSDs	B-Device
.	O
</s>
<s>
Performance	O
of	O
flash-based	O
SSDs	B-Device
is	O
difficult	O
to	O
benchmark	O
because	O
of	O
the	O
wide	O
range	O
of	O
possible	O
conditions	O
.	O
</s>
<s>
In	O
a	O
test	O
performed	O
in	O
2010	O
by	O
Xssist	O
,	O
using	O
IOmeter	B-General_Concept
,	O
4kB	O
random	O
70%	O
read/30	O
%	O
write	O
,	O
queue	O
depth	O
4	O
,	O
the	O
IOPS	O
delivered	O
by	O
the	O
Intel	O
X25-E	O
64GB	O
G1	O
started	O
around	O
10,000	O
IOPs	O
,	O
and	O
dropped	O
sharply	O
after	O
8minutes	O
to	O
4,000	O
IOPS	O
,	O
and	O
continued	O
to	O
decrease	O
gradually	O
for	O
the	O
next	O
42minutes	O
.	O
</s>
<s>
Designers	O
of	O
enterprise-grade	O
flash	O
drives	O
try	O
to	O
extend	O
longevity	O
by	O
increasing	O
over-provisioning	O
and	O
by	O
employing	O
wear	B-Application
leveling	I-Application
.	O
</s>
<s>
Revenues	O
for	O
the	O
SSD	B-Device
market	O
(	O
including	O
low-cost	O
PC	O
solutions	O
)	O
worldwide	O
totalled	O
$585	O
million	O
in	O
2008	O
,	O
rising	O
over	O
100%	O
from	O
$259	O
million	O
in	O
2007	O
.	O
</s>
