<s>
A	O
disk	B-Device
enclosure	I-Device
is	O
a	O
specialized	O
casing	O
designed	O
to	O
hold	O
and	O
power	O
disk	B-General_Concept
drives	I-General_Concept
while	O
providing	O
a	O
mechanism	O
to	O
allow	O
them	O
to	O
communicate	O
to	O
one	O
or	O
more	O
separate	O
computers	O
.	O
</s>
<s>
Drive	B-Device
enclosures	I-Device
provide	O
power	O
to	O
the	O
drives	O
therein	O
and	O
convert	O
the	O
data	O
sent	O
across	O
their	O
native	O
data	B-General_Concept
bus	I-General_Concept
into	O
a	O
format	O
usable	O
by	O
an	O
external	O
connection	O
on	O
the	O
computer	O
to	O
which	O
it	O
is	O
connected	O
.	O
</s>
<s>
In	O
others	O
,	O
it	O
is	O
complicated	O
enough	O
to	O
require	O
a	O
separate	O
embedded	B-Architecture
system	I-Architecture
to	O
retransmit	O
data	O
over	O
connector	O
and	O
signal	O
of	O
a	O
different	O
standard	O
.	O
</s>
<s>
Factory-assembled	O
external	O
hard	B-Device
disk	I-Device
drives	I-Device
,	O
external	B-Device
DVD-ROM	I-Device
drives	O
,	O
and	O
others	O
consist	O
of	O
a	O
storage	O
device	O
in	O
a	O
disk	B-Device
enclosure	I-Device
.	O
</s>
<s>
Key	O
benefits	O
to	O
using	O
external	O
disk	B-Device
enclosures	I-Device
include	O
:	O
</s>
<s>
Adding	O
additional	O
storage	O
space	O
and	O
media	O
types	O
to	O
small	B-Device
form	I-Device
factor	I-Device
and	O
laptop	B-Device
computers	I-Device
,	O
as	O
well	O
as	O
sealed	O
embedded	B-Architecture
systems	I-Architecture
such	O
as	O
digital	B-Application
video	I-Application
recorders	I-Application
and	O
video	B-Device
game	I-Device
consoles	I-Device
.	O
</s>
<s>
Adding	O
more	O
drives	O
to	O
any	O
given	O
server	B-Application
or	O
workstation	O
than	O
their	O
chassis	O
can	O
hold	O
.	O
</s>
<s>
Using	O
a	O
network-attached	O
storage-capable	O
enclosure	O
over	O
a	O
network	B-Architecture
to	O
share	O
data	O
or	O
provide	O
a	O
cheap	O
off-site	O
backup	O
solution	O
.	O
</s>
<s>
Preventing	O
the	O
heat	O
from	O
a	O
disk	B-Device
drive	I-Device
from	O
increasing	O
the	O
heat	O
inside	O
an	O
operating	O
computer	B-General_Concept
case	I-General_Concept
.	O
</s>
<s>
Simple	O
and	O
cheap	O
approach	O
to	O
hot	B-Device
swapping	I-Device
.	O
</s>
<s>
Recovering	O
the	O
data	O
from	O
a	O
damaged	O
computer	O
's	O
hard	B-Device
drive	I-Device
,	O
particularly	O
when	O
it	O
does	O
not	O
share	O
the	O
same	O
interface	O
with	O
the	O
computer	O
used	O
to	O
perform	O
the	O
recovery	O
.	O
</s>
<s>
In	O
the	O
consumer	O
market	O
,	O
commonly	O
used	O
configurations	O
of	O
drive	B-Device
enclosures	I-Device
utilize	O
magnetic	B-Device
hard	I-Device
drives	I-Device
or	O
optical	O
disc	B-Device
drives	I-Device
inside	O
USB	B-Protocol
,	O
FireWire	B-Protocol
,	O
or	O
Serial	O
ATA	B-Protocol
enclosures	O
.	O
</s>
<s>
External	O
3.5-in	O
floppy	B-Device
drives	I-Device
are	O
also	O
fairly	O
common	O
,	O
following	O
a	O
trend	O
to	O
not	O
integrate	O
floppy	B-Device
drives	I-Device
into	O
compact	O
and	O
laptop	B-Device
computers	I-Device
.	O
</s>
<s>
Pre-built	O
external	B-Device
drives	I-Device
are	O
available	O
through	O
all	O
major	O
manufacturers	O
of	O
hard	B-Device
drives	I-Device
,	O
as	O
well	O
as	O
several	O
third	O
parties	O
.	O
</s>
<s>
These	O
may	O
also	O
be	O
referred	O
to	O
as	O
a	O
caddy	O
–	O
a	O
sheath	O
,	O
typically	O
plastic	O
or	O
metallic	O
,	O
within	O
which	O
a	O
hard	B-Device
disk	I-Device
drive	I-Device
can	O
be	O
placed	O
and	O
connected	O
with	O
the	O
same	O
type	O
of	O
adapters	O
as	O
a	O
conventional	O
motherboard	O
and	O
power	O
supply	O
would	O
use	O
.	O
</s>
<s>
power	O
;	O
most	O
variants	O
require	O
a	O
supply	O
,	O
unlike	O
CDs	B-Device
,	O
DVDs	O
and	O
USB	B-Protocol
flash	O
drives	O
...	O
</s>
<s>
Multiple	O
drives	O
:	O
RAID-enabled	O
enclosures	O
and	O
iSCSI	B-Protocol
enclosures	O
commonly	O
hold	O
multiple	O
drives	O
.	O
</s>
<s>
High-end	O
and	O
server-oriented	O
chassis	O
are	O
often	O
built	O
around	O
3.5-in	O
drives	O
in	O
hot-swappable	B-Device
drive	O
caddies	O
.	O
</s>
<s>
"	O
5.25-inch	O
"	O
drive	O
:	O
(	O
5.75	O
in	O
×	O
8	O
in	O
×	O
1.63	O
in	O
=	O
146.1mm	O
×	O
203mm	O
×	O
41.4mm	O
)	O
Most	O
desktop	O
models	O
of	O
drives	O
for	O
optical	O
120-mm	O
discs	O
(	O
DVD-ROM	O
or	O
CD-ROM	B-Device
drives	O
,	O
CD	B-Device
or	O
DVD	O
burners	O
)	O
,	O
are	O
designed	O
to	O
be	O
mounted	O
into	O
a	O
so-called	O
"	O
5.25-inch	O
slot	O
"	O
,	O
which	O
obtained	O
its	O
nickname	O
because	O
this	O
slot	O
size	O
was	O
initially	O
used	O
by	O
drives	O
for	O
floppy	B-Device
disks	I-Device
in	O
the	O
IBM	B-Operating_System
PC	I-Operating_System
AT	I-Operating_System
.	O
</s>
<s>
(	O
The	O
original	O
"	O
5.25-inch	O
slot	O
"	O
in	O
the	O
IBM	B-Device
PC	I-Device
was	O
with	O
3.25	O
in	O
(	O
82.6mm	O
)	O
twice	O
as	O
high	O
as	O
the	O
one	O
commonly	O
used	O
today	O
;	O
in	O
fact	O
,	O
the	O
PC	O
's	O
drive	O
size	O
was	O
called	O
"	O
5.25-inch	O
full-height	O
"	O
,	O
and	O
the	O
size	O
used	O
in	O
the	O
PC	B-Operating_System
AT	I-Operating_System
and	O
commonly	O
used	O
today	O
is	O
"	O
5.25-inch	O
half-height	O
"	O
.	O
)	O
</s>
<s>
"	O
3.5-inch	O
"	O
drive	O
:	O
(	O
4	O
in	O
×	O
5.75	O
in	O
×	O
1	O
in	O
=	O
101.6mm	O
×	O
146.05mm	O
×	O
25.4mm	O
)	O
This	O
smaller	O
,	O
disk-drive	O
form	O
factor	O
was	O
introduced	O
with	O
the	O
Apple	B-Device
Macintosh	I-Device
series	O
in	O
1984	O
,	O
and	O
later	O
adopted	O
throughout	O
the	O
industry	O
beginning	O
widely	O
with	O
the	O
IBM	B-Device
PS/2	I-Device
series	O
in	O
1987	O
,	O
which	O
included	O
drives	O
of	O
this	O
size	O
for	O
90-mm	O
(	O
"	O
3.5-inch	O
"	O
)	O
floppy	B-Device
disks	I-Device
.	O
</s>
<s>
This	O
form	O
factor	O
is	O
today	O
used	O
by	O
most	O
desktop	O
hard	B-Device
drives	I-Device
.	O
</s>
<s>
"	O
2.5-inch	O
"	O
drive	O
:	O
(	O
2.75	O
in	O
×	O
3.945	O
in	O
×	O
0.374	O
in	O
=	O
69.85mm	O
×	O
100.2mm	O
×	O
9.5mm	O
)	O
This	O
even	O
smaller	O
,	O
form	O
factor	O
is	O
widely	O
used	O
today	O
in	O
notebook	B-Device
computers	I-Device
and	O
similar	O
small-footprint	O
devices	O
.	O
</s>
<s>
This	O
enables	O
enclosure	O
vendors	O
to	O
power	O
the	O
devices	O
directly	O
from	O
the	O
host	O
device	O
's	O
USB	B-Protocol
or	O
other	O
external	O
bus	O
,	O
in	O
most	O
cases	O
.	O
</s>
<s>
"	O
1.8-inch	O
"	O
drive	O
:	O
Found	O
in	O
extremely	O
compact	O
devices	O
,	O
such	O
as	O
certain	O
portable	O
media	O
players	O
and	O
smaller	O
notebooks	B-Device
,	O
these	O
devices	O
are	O
not	O
standardized	O
like	O
their	O
2.5inch	O
cousins	O
.	O
</s>
<s>
While	O
laptop	B-Device
hard	I-Device
drives	I-Device
are	O
today	O
generally	O
of	O
the	O
9.5mm	O
high	O
variant	O
of	O
the	O
"	O
2.5-inch	O
"	O
drive	O
form	O
factor	O
,	O
older	O
laptops	B-Device
and	O
notebooks	B-Device
had	O
hard	B-Device
drives	I-Device
that	O
varied	O
in	O
height	O
,	O
which	O
can	O
make	O
it	O
difficult	O
to	O
find	O
a	O
well-fitting	O
chassis	O
.	O
</s>
<s>
Laptop	B-Device
optical	O
drives	O
require	O
"	O
slim	O
"	O
5.25-in	O
enclosures	O
,	O
since	O
they	O
have	O
approximately	O
half	O
the	O
thickness	O
of	O
their	O
desktop	O
counterparts	O
,	O
and	O
most	O
models	O
use	O
a	O
special	O
50-pin	O
connector	O
that	O
differs	O
from	O
the	O
40-pin	O
connectors	O
used	O
on	O
desktop	O
ATA	B-Protocol
drives	I-Protocol
.	O
</s>
<s>
While	O
they	O
are	O
less	O
common	O
now	O
than	O
they	O
once	O
were	O
,	O
it	O
is	O
also	O
possible	O
to	O
purchase	O
a	O
drive	O
chassis	O
and	O
mount	O
that	O
will	O
convert	O
a	O
3.5-inch	O
hard	B-Device
drive	I-Device
into	O
a	O
removable	O
hard	B-Device
disk	I-Device
that	O
can	O
be	O
plugged	O
into	O
and	O
removed	O
from	O
a	O
mounting	O
bracket	O
permanently	O
installed	O
in	O
a	O
desktop	O
PC	B-General_Concept
case	I-General_Concept
.	O
</s>
<s>
The	O
mounting	O
bracket	O
carries	O
the	O
data	B-General_Concept
bus	I-General_Concept
and	O
power	O
connections	O
over	O
a	O
proprietary	O
connector	O
,	O
and	O
converts	O
back	O
into	O
the	O
drive	O
's	O
native	O
data	B-General_Concept
bus	I-General_Concept
format	O
and	O
power	O
connections	O
inside	O
the	O
drive	O
's	O
chassis	O
.	O
</s>
<s>
In	O
enterprise	B-General_Concept
storage	I-General_Concept
the	O
term	O
refers	O
to	O
a	O
larger	O
physical	O
chassis	O
.	O
</s>
<s>
The	O
term	O
can	O
be	O
used	O
both	O
in	O
reference	O
to	O
network-attached	B-Application
storage	I-Application
(	O
NAS	B-Application
)	O
and	O
components	O
of	O
a	O
storage	O
area	O
network	B-Architecture
(	O
SAN	O
)	O
or	O
be	O
used	O
to	O
describe	O
a	O
chassis	O
directly	O
attached	O
to	O
one	O
or	O
more	O
servers	O
over	O
an	O
external	O
bus	O
.	O
</s>
<s>
Like	O
their	O
conventional	O
server	B-Application
brethren	O
,	O
these	O
devices	O
may	O
include	O
a	O
backplane	B-Architecture
,	O
temperature	O
sensors	B-Application
,	O
cooling	O
systems	O
,	O
enclosure	O
management	O
devices	O
,	O
and	O
redundant	O
power	O
supplies	O
.	O
</s>
<s>
SCSI	B-Architecture
,	O
SAS	O
,	O
Fibre	B-Architecture
Channel	I-Architecture
,	O
eSATAp	O
,	O
and	O
eSATA	O
interfaces	O
can	O
be	O
used	O
to	O
directly	O
connect	O
the	O
external	O
hard	B-Device
drive	I-Device
to	O
an	O
internal	O
host	B-Architecture
adapter	I-Architecture
,	O
without	O
the	O
need	O
for	O
any	O
intervening	O
controller	O
.	O
</s>
<s>
External	O
variants	O
of	O
these	O
native	O
drive	O
protocols	O
are	O
extremely	O
similar	O
to	O
the	O
internal	O
protocols	O
,	O
but	O
are	O
often	O
expanded	O
to	O
carry	O
power	O
(	O
such	O
as	O
eSATAp	O
and	O
the	O
SCSI	B-Architecture
Single	O
Connector	O
Attachment	O
)	O
and	O
to	O
use	O
a	O
more	O
durable	O
physical	O
connector	O
.	O
</s>
<s>
A	O
host	B-Architecture
adapter	I-Architecture
with	O
external	O
port	O
may	O
be	O
necessary	O
to	O
connect	O
a	O
drive	O
,	O
if	O
a	O
computer	O
lacks	O
an	O
available	O
external	O
port	O
.	O
</s>
<s>
USB	B-Protocol
or	O
FireWire	B-Protocol
connections	O
are	O
typically	O
used	O
to	O
attach	O
consumer	O
class	O
external	O
hard	B-Device
drives	I-Device
to	O
a	O
computer	O
.	O
</s>
<s>
Unlike	O
SCSI	B-Architecture
,	O
eSATA	O
,	O
or	O
SAS	O
these	O
require	O
circuitry	O
to	O
convert	O
the	O
hard	B-Device
disk	I-Device
's	O
native	O
signal	O
to	O
the	O
appropriate	O
protocol	O
.	O
</s>
<s>
Parallel	B-Protocol
ATA	I-Protocol
and	O
internal	O
Serial	O
ATA	B-Protocol
hard	B-Device
disks	I-Device
are	O
frequently	O
connected	O
to	O
such	O
chassis	O
because	O
nearly	O
all	O
computers	O
on	O
the	O
market	O
today	O
have	O
USB	B-Protocol
or	O
FireWire	B-Protocol
ports	I-Protocol
,	O
and	O
these	O
chassis	O
are	O
inexpensive	O
and	O
easy	O
to	O
find	O
.	O
</s>
<s>
iSCSI	B-Protocol
,	O
NFS	B-Protocol
,	O
or	O
CIFS	B-Operating_System
are	O
all	O
commonly	O
used	O
protocols	O
that	O
are	O
used	O
to	O
allow	O
an	O
external	O
hard	B-Device
drive	I-Device
to	O
use	O
a	O
network	B-Architecture
to	O
send	O
data	O
to	O
a	O
computer	O
system	O
.	O
</s>
<s>
This	O
type	O
of	O
external	O
hard	B-Device
drive	I-Device
is	O
also	O
known	O
as	O
Network-attached	B-Application
storage	I-Application
or	O
NAS	B-Application
.	O
</s>
<s>
Often	O
,	O
such	O
drives	O
are	O
embedded	B-Architecture
computers	I-Architecture
running	O
operating	O
systems	O
such	O
as	O
Linux	B-Application
or	O
VxWorks	B-Operating_System
that	O
use	O
their	O
NFS	B-Protocol
daemons	O
and	O
SAMBA	B-Language
to	O
provide	O
a	O
networked	O
file	O
system	O
.	O
</s>
<s>
A	O
newer	O
technology	O
NAS	B-Application
,	O
has	O
been	O
applied	O
to	O
some	O
disk	B-Device
enclosures	I-Device
,	O
which	O
allows	O
network	B-Architecture
ability	O
,	O
direct	O
connection	O
(	O
e.g.	O
,	O
USB	B-Protocol
)	O
and	O
even	O
RAID	O
features	O
.	O
</s>
<s>
"	O
Shucking	O
"	O
refers	O
to	O
the	O
process	O
of	O
purchasing	O
an	O
external	O
hard	B-Device
disk	I-Device
drive	I-Device
and	O
removing	O
the	O
drive	O
from	O
its	O
enclosure	O
,	O
in	O
order	O
for	O
it	O
to	O
be	O
used	O
as	O
an	O
internal	O
disk	B-Device
drive	I-Device
.	O
</s>
<s>
This	O
is	O
performed	O
because	O
external	B-Device
drives	I-Device
are	O
often	O
cheaper	O
than	O
internal	O
drives	O
of	O
the	O
same	O
capacity	O
and	O
model	O
,	O
and	O
that	O
external	B-Device
drives	I-Device
designed	O
for	O
continuous	O
usage	O
often	O
contain	O
hard	B-Device
drives	I-Device
designed	O
for	O
increased	O
reliability	O
.	O
</s>
<s>
Following	O
the	O
hard	B-Device
disk	I-Device
drive	I-Device
shortages	O
caused	O
by	O
the	O
2011	O
Thailand	O
floods	O
,	O
data	B-General_Concept
storage	I-General_Concept
company	O
Backblaze	B-General_Concept
reduced	O
its	O
cost	O
of	O
acquiring	O
hard	B-Device
drives	I-Device
by	O
purchasing	O
external	O
hard	B-Device
drives	I-Device
and	O
shucking	O
them	O
.	O
</s>
<s>
According	O
to	O
Backblaze	B-General_Concept
Chief	O
Executive	O
Gleb	O
Budman	O
,	O
the	O
company	O
purchased	O
1,838	O
external	B-Device
drives	I-Device
during	O
this	O
period	O
.	O
</s>
<s>
Describing	O
the	O
process	O
as	O
"	O
drive	O
farming	O
"	O
,	O
the	O
company	O
noted	O
that	O
it	O
was	O
much	O
cheaper	O
for	O
them	O
to	O
purchase	O
3	O
TB	O
external	B-Device
drives	I-Device
and	O
removing	O
them	O
from	O
their	O
cases	O
manually	O
,	O
than	O
it	O
is	O
to	O
purchase	O
internal	O
drives	O
.	O
</s>
