<s>
The	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
device	I-Architecture
class	I-Architecture
(	O
also	O
known	O
as	O
USB	B-Architecture
MSC	I-Architecture
or	O
UMS	O
)	O
is	O
a	O
set	O
of	O
computing	O
communications	O
protocols	O
,	O
specifically	O
a	O
USB	B-Protocol
Device	O
Class	O
,	O
defined	O
by	O
the	O
USB	B-Protocol
Implementers	O
Forum	O
that	O
makes	O
a	O
USB	B-Protocol
device	O
accessible	O
to	O
a	O
host	O
computing	O
device	O
and	O
enables	O
file	O
transfers	O
between	O
the	O
host	O
and	O
the	O
USB	B-Protocol
device	O
.	O
</s>
<s>
To	O
a	O
host	O
,	O
the	O
USB	B-Protocol
device	O
acts	O
as	O
an	O
external	O
hard	B-Device
drive	I-Device
;	O
the	O
protocol	O
set	O
interfaces	O
with	O
a	O
number	O
of	O
storage	O
devices	O
.	O
</s>
<s>
Most	O
mainstream	O
operating	B-General_Concept
systems	I-General_Concept
include	O
support	O
for	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
devices	I-Architecture
;	O
support	O
on	O
older	O
systems	O
is	O
usually	O
available	O
through	O
patches	O
.	O
</s>
<s>
Microsoft	O
Windows	O
has	O
supported	O
MSC	O
since	O
Windows	B-Application
2000	I-Application
.	O
</s>
<s>
There	O
is	O
no	O
support	O
for	O
USB	B-Protocol
supplied	O
by	O
Microsoft	O
in	O
Windows	O
before	O
Windows	B-Application
95	I-Application
and	O
Windows	B-Device
NT	I-Device
4.0	I-Device
.	O
</s>
<s>
Windows	B-Application
95	I-Application
OSR2.1	O
,	O
an	O
update	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
featured	O
limited	O
support	O
for	O
USB	B-Protocol
.	O
</s>
<s>
During	O
that	O
time	O
no	O
generic	O
USB	B-Protocol
mass-storage	O
driver	O
was	O
produced	O
by	O
Microsoft	O
(	O
including	O
for	O
Windows	B-Device
98	I-Device
)	O
,	O
and	O
a	O
device-specific	O
driver	O
was	O
needed	O
for	O
each	O
type	O
of	O
USB	B-Architecture
storage	I-Architecture
device	O
.	O
</s>
<s>
Third-party	O
,	O
freeware	O
drivers	O
became	O
available	O
for	O
Windows	B-Device
98	I-Device
and	O
Windows	O
98SE	O
,	O
and	O
third-party	O
drivers	O
are	O
also	O
available	O
for	O
Windows	B-Device
NT	I-Device
4.0	I-Device
.	O
</s>
<s>
Windows	B-Application
2000	I-Application
has	O
support	O
(	O
via	O
a	O
generic	O
driver	O
)	O
for	O
standard	O
USB	B-Protocol
mass-storage	O
devices	O
;	O
Windows	B-Device
Me	I-Device
and	O
all	O
later	O
Windows	O
versions	O
also	O
include	O
support	O
.	O
</s>
<s>
Windows	B-Operating_System
Mobile	I-Operating_System
supports	O
accessing	O
most	O
USB	B-Protocol
mass-storage	O
devices	O
formatted	O
with	O
FAT	B-Application
on	O
devices	O
with	O
USB	B-Protocol
Host	O
.	O
</s>
<s>
However	O
,	O
portable	O
devices	O
typically	O
cannot	O
provide	O
enough	O
power	O
for	O
hard-drive	B-Device
disk	B-Device
enclosures	I-Device
(	O
a	O
hard	B-Device
drive	I-Device
typically	O
requires	O
the	O
maximum	O
2.5W	O
in	O
the	O
USB	B-Protocol
specification	O
)	O
without	O
a	O
self-powered	O
USB	B-Protocol
hub	O
.	O
</s>
<s>
A	O
Windows	B-Operating_System
Mobile	I-Operating_System
device	O
cannot	O
display	O
its	O
file	B-Application
system	I-Application
as	O
a	O
mass-storage	O
device	O
unless	O
the	O
device	O
implementer	O
adds	O
that	O
functionality	O
.	O
</s>
<s>
Only	O
memory	B-Device
cards	I-Device
(	O
not	O
internal-storage	O
memory	O
)	O
can	O
generally	O
be	O
exported	O
,	O
due	O
to	O
file-systems	B-Application
issues	O
;	O
see	O
device	O
access	O
,	O
below	O
.	O
</s>
<s>
The	O
AutoRun	O
feature	O
of	O
Windows	O
worked	O
on	O
all	O
removable	O
media	O
,	O
allowing	O
USB	B-Architecture
storage	I-Architecture
devices	O
to	O
become	O
a	O
portal	O
for	O
computer	O
viruses	O
.	O
</s>
<s>
Beginning	O
with	O
Windows	O
7	O
,	O
Microsoft	O
limited	O
AutoRun	O
to	O
CD	B-Device
and	O
DVD	O
drives	O
,	O
updating	O
previous	O
Windows	O
versions	O
.	O
</s>
<s>
Neither	O
MS-DOS	B-Application
nor	O
most	O
compatible	O
operating	B-General_Concept
systems	I-General_Concept
included	O
support	O
for	O
USB	B-Protocol
.	O
</s>
<s>
Third-party	O
generic	O
drivers	O
,	O
such	O
as	O
Duse	O
,	O
USBASPI	O
and	O
DOSUSB	O
,	O
are	O
available	O
to	O
support	O
USB	B-Protocol
mass-storage	O
devices	O
.	O
</s>
<s>
FreeDOS	B-Application
supports	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
as	O
an	O
Advanced	B-Application
SCSI	I-Application
Programming	I-Application
Interface	I-Application
(	O
ASPI	B-Application
)	O
interface	O
.	O
</s>
<s>
Apple	O
Computer	O
's	O
Mac	B-Operating_System
OS	I-Operating_System
9	I-Operating_System
and	O
macOS	B-Application
support	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
;	O
Mac	B-Application
OS	I-Application
8.5.1	O
supported	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
through	O
an	O
optional	O
driver	O
.	O
</s>
<s>
The	O
Linux	B-Operating_System
kernel	I-Operating_System
has	O
supported	O
USB	B-Protocol
mass-storage	O
devices	O
since	O
its	O
2.4	O
series	O
(	O
2001	O
)	O
,	O
and	O
a	O
backport	O
to	O
kernel	B-Operating_System
2.2.18	O
has	O
been	O
made	O
.	O
</s>
<s>
In	O
Linux	B-Application
,	O
more	O
features	O
exist	O
in	O
addition	O
to	O
the	O
generic	O
drivers	O
for	O
USB	B-Architecture
mass-storage	I-Architecture
device	I-Architecture
class	I-Architecture
devices	O
,	O
including	O
quirks	O
,	O
bug	O
fixes	O
and	O
additional	O
functionality	O
for	O
devices	O
and	O
controllers	O
(	O
vendor-enabled	O
functions	O
such	O
as	O
ATA	B-Protocol
command	O
pass-through	O
for	O
ATA-USB	O
bridges	O
,	O
which	O
is	O
useful	O
for	O
S.M.A.R.T.	O
</s>
<s>
or	O
temperature	O
monitoring	O
,	O
controlling	O
the	O
spin-up	O
and	O
spin-down	O
of	O
hard	B-Device
disk	I-Device
drives	I-Device
,	O
and	O
other	O
options	O
)	O
.	O
</s>
<s>
This	O
includes	O
a	O
certain	O
portion	O
of	O
Android-based	O
devices	O
,	O
through	O
support	O
of	O
USB-OTG	O
,	O
since	O
Android	B-Application
uses	O
the	O
Linux	B-Operating_System
kernel	I-Operating_System
.	O
</s>
<s>
Solaris	B-Application
has	O
supported	O
devices	O
since	O
its	O
version	O
2.8	O
(	O
1998	O
)	O
,	O
NetBSD	B-Device
since	O
its	O
version	O
1.5	O
(	O
2000	O
)	O
,	O
FreeBSD	B-Operating_System
since	O
its	O
version	O
4.0	O
(	O
2000	O
)	O
and	O
OpenBSD	B-Operating_System
since	O
its	O
version	O
2.7	O
(	O
2000	O
)	O
.	O
</s>
<s>
Digital	B-Operating_System
UNIX	I-Operating_System
(	O
later	O
known	O
as	O
Tru64	B-Operating_System
UNIX	I-Operating_System
)	O
,	O
has	O
supported	O
USB	B-Protocol
and	O
USB	B-Protocol
mass-storage	O
devices	O
since	O
its	O
version	O
4.0E	O
(	O
1998	O
)	O
.	O
</s>
<s>
AIX	B-Application
has	O
supported	O
USB	B-Protocol
mass-storage	O
devices	O
since	O
its	O
5.3	O
T9	O
and	O
6.1	O
T3	O
versions	O
;	O
however	O
,	O
it	O
is	O
not	O
well-supported	O
and	O
lacks	O
features	O
such	O
as	O
partitioning	O
and	O
general	O
blocking	O
.	O
</s>
<s>
The	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
and	O
PlayStation	B-Operating_System
3	I-Operating_System
support	O
most	O
mass-storage	O
devices	O
for	O
the	O
data	O
transfer	O
of	O
media	O
such	O
as	O
pictures	O
and	O
music	O
.	O
</s>
<s>
As	O
of	O
April	O
2010	O
,	O
the	B-Operating_System
Xbox	I-Operating_System
360	I-Operating_System
(	O
a	O
)	O
used	O
a	O
mass-storage	O
device	O
for	O
saved	O
games	O
and	O
the	B-Operating_System
PS3	I-Operating_System
allowed	O
transfers	O
between	O
devices	O
on	O
a	O
mass-storage	O
device	O
.	O
</s>
<s>
Independent	O
developers	O
have	O
released	O
drivers	O
for	O
the	O
TI-84	B-Device
Plus	I-Device
and	O
TI-84	B-Device
Plus	I-Device
Silver	I-Device
Edition	I-Device
to	O
access	O
USB	B-Protocol
mass-storage	O
devices	O
.	O
</s>
<s>
In	O
these	O
calculators	O
,	O
the	O
usb8x	B-Application
driver	O
supports	O
the	O
msd8x	O
user-interface	O
application	O
.	O
</s>
<s>
The	O
USB	B-Protocol
mass-storage	O
specification	O
provides	O
an	O
interface	O
to	O
a	O
number	O
of	O
industry-standard	O
command	O
sets	O
,	O
allowing	O
a	O
device	O
to	O
disclose	O
its	O
subclass	O
.	O
</s>
<s>
In	O
practice	O
,	O
there	O
is	O
little	O
support	O
for	O
specifying	O
a	O
command	O
set	O
via	O
its	O
subclass	O
;	O
most	O
drivers	O
only	O
support	O
the	O
SCSI	B-Architecture
transparent	O
command	O
set	O
,	O
designating	O
their	O
subset	O
of	O
the	O
SCSI	B-Architecture
command	O
set	O
with	O
their	O
SCSI	B-Architecture
Peripheral	O
Device	O
Type	O
(	O
PDT	O
)	O
.	O
</s>
<s>
The	O
specification	O
does	O
not	O
require	O
a	O
particular	O
file	B-Application
system	I-Application
on	O
conforming	O
devices	O
.	O
</s>
<s>
Based	O
on	O
the	O
specified	O
command	O
set	O
and	O
any	O
subset	O
,	O
it	O
provides	O
a	O
means	O
to	O
read	O
and	O
write	O
sectors	O
of	O
data	O
(	O
similar	O
to	O
the	O
low-level	O
interface	O
used	O
to	O
access	O
a	O
hard	B-Device
drive	I-Device
)	O
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
may	O
treat	O
a	O
USB	B-Protocol
mass-storage	O
device	O
like	O
a	O
hard	B-Device
drive	I-Device
;	O
users	O
may	O
partition	O
it	O
in	O
any	O
format	O
(	O
such	O
as	O
MBR	O
and	O
GPT	O
)	O
,	O
and	O
format	O
it	O
with	O
any	O
file	B-Application
system	I-Application
.	O
</s>
<s>
Because	O
of	O
its	O
relative	O
simplicity	O
,	O
the	O
most	O
common	O
file	B-Application
system	I-Application
on	O
embedded	B-Architecture
devices	I-Architecture
such	O
as	O
USB	B-Protocol
flash	O
drives	O
,	O
cameras	O
,	O
or	O
digital	O
audio	O
players	O
is	O
Microsoft	O
's	O
FAT	B-Application
or	O
FAT32	B-Application
file	B-Application
system	I-Application
(	O
with	O
optional	O
support	O
for	O
long	O
filenames	O
)	O
.	O
</s>
<s>
Large	O
,	O
USB-based	O
hard	B-Device
disks	I-Device
may	O
be	O
formatted	O
with	O
NTFS	B-Application
,	O
which	O
(	O
except	O
for	O
Windows	O
)	O
is	O
less	O
supported	O
.	O
</s>
<s>
However	O
,	O
a	O
keydrive	O
or	O
other	O
device	O
may	O
be	O
formatted	O
with	O
another	O
file	B-Application
system	I-Application
(	O
HFS	B-Application
Plus	I-Application
on	O
an	O
Apple	B-Device
Macintosh	I-Device
,	O
or	O
Ext2	B-Application
on	O
Linux	B-Application
,	O
or	O
Unix	B-Operating_System
File	I-Operating_System
System	I-Operating_System
on	O
Solaris	B-Application
or	O
BSD	O
)	O
.	O
</s>
<s>
This	O
choice	O
may	O
limit	O
(	O
or	O
prevent	O
)	O
access	O
to	O
a	O
device	O
's	O
contents	O
by	O
equipment	O
using	O
a	O
different	O
operating	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
OS-dependent	O
storage	O
options	O
include	O
LVM	B-Application
,	O
partition	O
tables	O
and	O
software	O
encryption	O
.	O
</s>
<s>
In	O
cameras	O
,	O
MP3	O
players	O
and	O
similar	O
devices	O
which	O
must	O
access	O
a	O
file	B-Application
system	I-Application
independent	O
of	O
an	O
external	O
host	O
,	O
the	O
FAT32	B-Application
file	B-Application
system	I-Application
is	O
preferred	O
by	O
manufacturers	O
.	O
</s>
<s>
All	O
such	O
devices	O
halt	O
their	O
file-system	B-Application
(	O
dismount	B-Device
)	O
before	O
making	O
it	O
available	O
to	O
a	O
host	O
operating	B-General_Concept
system	I-General_Concept
to	O
prevent	O
file-system	B-Application
corruption	O
or	O
other	O
damage	O
(	O
although	O
it	O
is	O
theoretically	O
possible	O
for	O
both	O
devices	O
to	O
use	O
read-only	O
mode	O
or	O
a	O
cluster	B-Application
file	I-Application
system	I-Application
)	O
.	O
</s>
<s>
One	O
puts	O
the	O
file	B-Application
system	I-Application
(	O
usually	O
FAT32	B-Application
)	O
directly	O
on	O
the	O
device	O
without	O
partitioning	O
,	O
making	O
it	O
start	O
from	O
sector	O
0	O
without	O
additional	O
boot	O
sectors	O
,	O
headers	B-General_Concept
or	O
partitions	O
.	O
</s>
<s>
This	O
partition	O
is	O
often	O
aligned	O
to	O
a	O
high	O
power	O
of	O
two	O
of	O
the	O
sectors	O
(	O
such	O
as	O
1	O
or	O
2MB	O
)	O
,	O
common	O
in	O
solid	B-Device
state	I-Device
drives	I-Device
for	O
performance	O
and	O
durability	O
.	O
</s>
<s>
Some	O
devices	O
with	O
embedded	O
storage	O
resembling	O
a	O
USB	B-Protocol
mass-storage	O
device	O
(	O
such	O
as	O
MP3	O
players	O
with	O
a	O
USB	B-Protocol
port	O
)	O
will	O
report	O
a	O
damaged	O
(	O
or	O
missing	O
)	O
file	B-Application
system	I-Application
if	O
they	O
are	O
reformatted	O
with	O
a	O
different	O
file	B-Application
system	I-Application
.	O
</s>
<s>
However	O
,	O
most	O
default-partition	O
devices	O
may	O
be	O
repartitioned	O
(	O
by	O
reducing	O
the	O
first	O
partition	O
and	O
file	B-Application
system	I-Application
)	O
with	O
additional	O
partitions	O
.	O
</s>
<s>
Devices	O
connected	O
by	O
a	O
single	O
USB	B-Protocol
port	O
may	O
function	O
as	O
multiple	O
USB	B-Protocol
devices	O
,	O
one	O
of	O
which	O
is	O
a	O
USB	B-Protocol
mass-storage	O
device	O
.	O
</s>
<s>
This	O
simplifies	O
distribution	O
and	O
access	O
to	O
drivers	O
and	O
documentation	O
,	O
primarily	O
for	O
the	O
Microsoft	O
Windows	O
and	O
Mac	B-Application
OS	I-Application
X	O
operating	B-General_Concept
systems	I-General_Concept
.	O
</s>
<s>
Such	O
drivers	O
are	O
required	O
to	O
make	O
full	O
use	O
of	O
the	O
device	O
,	O
usually	O
because	O
it	O
does	O
not	O
fit	O
a	O
standard	O
USB	B-Protocol
class	O
or	O
has	O
additional	O
functionality	O
.	O
</s>
<s>
An	O
embedded	O
USB	B-Protocol
mass-storage	O
device	O
makes	O
it	O
possible	O
to	O
install	O
additional	O
drivers	O
without	O
CD-ROM	O
disks	O
,	O
floppies	O
or	O
Internet	O
access	O
to	O
a	O
vendor	O
website	O
;	O
this	O
is	O
important	O
,	O
since	O
many	O
modern	O
systems	O
are	O
supplied	O
without	O
optical	O
or	O
floppy	O
drives	O
.	O
</s>
<s>
The	O
embedded	O
USB	B-Architecture
mass	I-Architecture
storage	I-Architecture
is	O
usually	O
made	O
permanently	O
read-only	O
by	O
the	O
vendor	O
,	O
preventing	O
accidental	O
corruption	O
and	O
use	O
for	O
other	O
purposes	O
(	O
although	O
it	O
may	O
be	O
updated	O
with	O
proprietary	O
protocols	O
when	O
performing	O
a	O
firmware	O
upgrade	O
)	O
.	O
</s>
<s>
Some	O
advanced	O
hard	B-Device
disk	I-Device
drive	I-Device
commands	O
,	O
such	O
as	O
Tagged	O
Command	O
Queuing	O
and	O
Native	O
Command	O
Queuing	O
(	O
which	O
may	O
increase	O
performance	O
)	O
,	O
ATA	B-Protocol
Secure	O
Erase	O
(	O
which	O
allows	O
all	O
data	O
on	O
the	O
drive	O
to	O
be	O
securely	O
erased	O
)	O
and	O
S.M.A.R.T.	O
</s>
<s>
(	O
accessing	O
indicators	O
of	O
drive	O
reliability	O
)	O
exist	O
as	O
extensions	O
to	O
low-level	O
drive	O
command	O
sets	O
such	O
as	O
SCSI	B-Architecture
,	O
ATA	B-Protocol
and	O
ATAPI	O
.	O
</s>
<s>
These	O
features	O
may	O
not	O
work	O
when	O
the	O
drives	O
are	O
placed	O
in	O
a	O
disk	B-Device
enclosure	I-Device
that	O
supports	O
a	O
USB	B-Protocol
mass-storage	O
interface	O
.	O
</s>
<s>
Some	O
USB	B-Protocol
mass-storage	O
interfaces	O
are	O
generic	O
,	O
providing	O
basic	O
read-write	O
commands	O
;	O
although	O
that	O
works	O
well	O
for	O
basic	O
data	O
transfers	O
with	O
devices	O
containing	O
hard	B-Device
drives	I-Device
,	O
there	O
is	O
no	O
simple	O
way	O
to	O
send	O
advanced	O
,	O
device-specific	O
commands	O
to	O
such	O
USB	B-Protocol
mass-storage	O
devices	O
(	O
though	O
,	O
devices	O
may	O
create	O
their	O
own	O
communication	O
protocols	O
over	O
a	O
standard	O
USB	B-Protocol
control	O
interface	O
)	O
.	O
</s>
<s>
The	O
USB	B-Protocol
Attached	O
SCSI	B-Architecture
(	O
UAS	O
)	O
protocol	O
,	O
introduced	O
in	O
USB3.0	O
,	O
fixes	O
several	O
of	O
these	O
issues	O
,	O
including	O
command	O
queuing	O
,	O
command	O
pipes	O
for	O
hardware	O
requiring	O
them	O
,	O
and	O
power	O
management	O
.	O
</s>
<s>
Specific	O
USB2.0	O
chipsets	O
had	O
proprietary	O
methods	O
of	O
achieving	O
SCSI	B-Architecture
pass-through	O
,	O
which	O
could	O
be	O
used	O
to	O
read	O
S.M.A.R.T.	O
</s>
<s>
data	O
from	O
drives	O
using	O
tools	O
such	O
as	O
smartctl	B-Language
(	O
using	O
the	O
option	O
followed	O
by	O
"	O
chipset	O
"	O
)	O
.	O
</s>
<s>
More	O
recent	O
USB	B-Architecture
storage	I-Architecture
chipsets	O
support	O
the	O
SCSI	B-Architecture
/	O
ATA	B-Protocol
Translation	O
(	O
SAT	O
)	O
as	O
a	O
generic	O
protocol	O
for	O
interacting	O
with	O
ATA	B-Protocol
(	O
and	O
SATA	O
)	O
devices	O
.	O
</s>
<s>
Using	O
esoteric	O
ATA	B-Protocol
or	O
SCSI	B-Architecture
pass-through	O
commands	O
(	O
such	O
as	O
secure-erase	O
or	O
password	O
protection	O
)	O
when	O
a	O
drive	O
is	O
connected	O
via	O
a	O
USB	B-Protocol
bridge	O
may	O
cause	O
drive	O
failure	O
,	O
especially	O
with	O
the	O
hdparm	B-Application
utility	O
.	O
</s>
