<s>
In	O
computing	O
,	O
a	O
file	B-Application
server	I-Application
(	O
or	O
fileserver	B-Application
)	O
is	O
a	O
computer	O
attached	O
to	O
a	O
network	O
that	O
provides	O
a	O
location	O
for	O
shared	O
disk	O
access	O
,	O
i.e.	O
</s>
<s>
storage	O
of	O
computer	O
files	O
(	O
such	O
as	O
text	O
,	O
image	O
,	O
sound	O
,	O
video	O
)	O
that	O
can	O
be	O
accessed	O
by	O
the	O
workstations	O
that	O
are	O
able	O
to	O
reach	O
the	O
computer	O
that	O
shares	O
the	O
access	O
through	O
a	O
computer	B-Architecture
network	I-Architecture
.	O
</s>
<s>
The	O
term	O
server	O
highlights	O
the	O
role	O
of	O
the	O
machine	O
in	O
the	O
traditional	O
client	B-Operating_System
–	I-Operating_System
server	I-Operating_System
scheme	O
,	O
where	O
the	O
clients	O
are	O
the	O
workstations	O
using	O
the	O
storage	O
.	O
</s>
<s>
A	O
file	B-Application
server	I-Application
does	O
not	O
normally	O
perform	O
computational	O
tasks	O
or	O
run	O
programs	O
on	O
behalf	O
of	O
its	O
client	O
workstations	O
.	O
</s>
<s>
File	B-Application
servers	I-Application
are	O
commonly	O
found	O
in	O
schools	O
and	O
offices	O
,	O
where	O
users	O
use	O
a	O
local	B-General_Concept
area	I-General_Concept
network	I-General_Concept
to	O
connect	O
their	O
client	O
computers	O
.	O
</s>
<s>
A	O
file	B-Application
server	I-Application
may	O
be	O
dedicated	O
or	O
non-dedicated	O
.	O
</s>
<s>
A	O
dedicated	O
server	O
is	O
designed	O
specifically	O
for	O
use	O
as	O
a	O
file	B-Application
server	I-Application
,	O
with	O
workstations	O
attached	O
for	O
reading	O
and	O
writing	O
files	O
and	O
databases	O
.	O
</s>
<s>
File	B-Application
servers	I-Application
may	O
also	O
be	O
categorized	O
by	O
the	O
method	O
of	O
access	O
:	O
Internet	O
file	B-Application
servers	I-Application
are	O
frequently	O
accessed	O
by	O
File	B-Protocol
Transfer	I-Protocol
Protocol	I-Protocol
or	O
by	O
HTTP	B-Protocol
(	O
but	O
are	O
different	O
from	O
,	O
that	O
often	O
provide	O
dynamic	O
web	O
content	O
in	O
addition	O
to	O
static	O
files	O
)	O
.	O
</s>
<s>
Servers	O
on	O
a	O
LAN	B-General_Concept
are	O
usually	O
accessed	O
by	O
SMB/CIFS	B-Operating_System
protocol	O
(	O
Windows	B-Application
and	O
Unix-like	B-Operating_System
)	O
or	O
NFS	B-Protocol
protocol	I-Protocol
(	O
Unix-like	B-Operating_System
systems	I-Operating_System
)	O
.	O
</s>
<s>
Database	B-Application
servers	I-Application
,	O
that	O
provide	O
access	O
to	O
a	O
shared	O
database	O
via	O
a	O
database	O
device	O
driver	O
,	O
are	O
not	O
regarded	O
as	O
file	B-Application
servers	I-Application
even	O
when	O
the	O
database	O
is	O
stored	O
in	O
files	O
,	O
as	O
they	O
are	O
not	O
designed	O
to	O
provide	O
those	O
files	O
to	O
users	O
and	O
tend	O
to	O
have	O
differing	O
technical	O
requirements	O
.	O
</s>
<s>
In	O
modern	O
businesses	O
,	O
the	O
design	O
of	O
file	B-Application
servers	I-Application
is	O
complicated	O
by	O
competing	O
demands	O
for	O
storage	O
space	O
,	O
access	O
speed	O
,	O
recoverability	O
,	O
ease	O
of	O
administration	O
,	O
security	O
,	O
and	O
budget	O
.	O
</s>
<s>
This	O
is	O
further	O
complicated	O
by	O
a	O
constantly	O
changing	O
environment	O
,	O
where	O
new	O
hardware	O
and	O
technology	O
rapidly	O
obsolesces	O
old	O
equipment	O
,	O
and	O
yet	O
must	O
seamlessly	O
come	O
online	O
in	O
a	O
fashion	O
compatible	B-Device
with	O
the	O
older	O
machinery	O
.	O
</s>
<s>
To	O
manage	O
throughput	O
,	O
peak	O
loads	O
,	O
and	O
response	B-Application
time	I-Application
,	O
vendors	O
may	O
utilize	O
queuing	O
theory	O
to	O
model	O
how	O
the	O
combination	O
of	O
hardware	O
and	O
software	O
will	O
respond	O
over	O
various	O
levels	O
of	O
demand	O
.	O
</s>
<s>
Servers	O
may	O
also	O
employ	O
dynamic	O
load	B-Application
balancing	I-Application
scheme	O
to	O
distribute	O
requests	O
across	O
various	O
pieces	O
of	O
hardware	O
.	O
</s>
<s>
The	O
primary	O
piece	O
of	O
hardware	O
equipment	O
for	O
servers	O
over	O
the	O
last	O
couple	O
of	O
decades	O
has	O
proven	O
to	O
be	O
the	O
hard	B-Device
disk	I-Device
drive	I-Device
.	O
</s>
<s>
Although	O
other	O
forms	O
of	O
storage	O
are	O
viable	O
(	O
such	O
as	O
magnetic	O
tape	O
and	O
solid-state	B-Device
drives	I-Device
)	O
disk	O
drives	O
have	O
continued	O
to	O
offer	O
the	O
best	O
fit	O
for	O
cost	O
,	O
performance	O
,	O
and	O
capacity	O
.	O
</s>
<s>
Since	O
the	O
crucial	O
function	O
of	O
a	O
file	B-Application
server	I-Application
is	O
storage	O
,	O
technology	O
has	O
been	O
developed	O
to	O
operate	O
multiple	O
disk	O
drives	O
together	O
as	O
a	O
team	O
,	O
forming	O
a	O
disk	B-General_Concept
array	I-General_Concept
.	O
</s>
<s>
A	O
disk	B-General_Concept
array	I-General_Concept
typically	O
has	O
cache	B-General_Concept
(	O
temporary	O
memory	O
storage	O
that	O
is	O
faster	O
than	O
the	O
magnetic	O
disks	O
)	O
,	O
as	O
well	O
as	O
advanced	O
functions	O
like	O
RAID	B-Architecture
and	O
storage	B-Application
virtualization	I-Application
.	O
</s>
<s>
Typically	O
disk	B-General_Concept
arrays	I-General_Concept
increase	O
level	O
of	O
availability	O
by	O
using	O
redundant	O
components	O
other	O
than	O
RAID	B-Architecture
,	O
such	O
as	O
power	O
supplies	O
.	O
</s>
<s>
Disk	B-General_Concept
arrays	I-General_Concept
may	O
be	O
consolidated	O
or	O
virtualized	O
in	O
a	O
SAN	O
.	O
</s>
<s>
Network-attached	B-Application
storage	I-Application
(	O
NAS	B-Application
)	O
is	O
file-level	O
computer	B-General_Concept
data	I-General_Concept
storage	I-General_Concept
connected	O
to	O
a	O
computer	B-Architecture
network	I-Architecture
providing	O
data	O
access	O
to	O
a	O
heterogeneous	O
group	O
of	O
clients	O
.	O
</s>
<s>
NAS	B-Application
devices	O
specifically	O
are	O
distinguished	O
from	O
file	B-Application
servers	I-Application
generally	O
in	O
a	O
NAS	B-Application
being	O
a	O
computer	B-Architecture
appliance	I-Architecture
–	O
a	O
specialized	O
computer	O
built	O
from	O
the	O
ground	O
up	O
for	O
serving	O
files	O
–	O
rather	O
than	O
a	O
general	O
purpose	O
computer	O
being	O
used	O
for	O
serving	O
files	O
(	O
possibly	O
with	O
other	O
functions	O
)	O
.	O
</s>
<s>
In	O
discussions	O
of	O
NASs	O
,	O
the	O
term	O
"	O
file	B-Application
server	I-Application
"	O
generally	O
stands	O
for	O
a	O
contrasting	O
term	O
,	O
referring	O
to	O
general	O
purpose	O
computers	O
only	O
.	O
</s>
<s>
NAS	B-Application
devices	O
are	O
gaining	O
popularity	O
,	O
offering	O
a	O
convenient	O
method	O
for	O
sharing	O
files	O
between	O
multiple	O
computers	O
.	O
</s>
<s>
Potential	O
benefits	O
of	O
network-attached	B-Application
storage	I-Application
,	O
compared	O
to	O
non-dedicated	O
file	B-Application
servers	I-Application
,	O
include	O
faster	O
data	O
access	O
,	O
easier	O
administration	O
,	O
and	O
simple	O
configuration	O
.	O
</s>
<s>
NAS	B-Application
systems	O
are	O
networked	O
appliances	B-Architecture
containing	O
one	O
or	O
more	O
hard	B-Device
drives	I-Device
,	O
often	O
arranged	O
into	O
logical	O
,	O
redundant	O
storage	O
containers	O
or	O
RAID	B-Architecture
arrays	I-Architecture
.	O
</s>
<s>
Network	B-Application
Attached	I-Application
Storage	I-Application
removes	O
the	O
responsibility	O
of	O
file	O
serving	O
from	O
other	O
servers	O
on	O
the	O
network	O
.	O
</s>
<s>
They	O
typically	O
provide	O
access	O
to	O
files	O
using	O
network	O
file	O
sharing	O
protocols	O
such	O
as	O
NFS	B-Protocol
,	O
SMB/CIFS	B-Operating_System
(	O
Server	B-Operating_System
Message	I-Operating_System
Block/Common	I-Operating_System
Internet	I-Operating_System
File	I-Operating_System
System	I-Operating_System
)	O
,	O
or	O
AFP	B-Protocol
.	O
</s>
<s>
File	B-Application
servers	I-Application
generally	O
offer	O
some	O
form	O
of	O
system	O
security	O
to	O
limit	O
access	O
to	O
files	O
to	O
specific	O
users	O
or	O
groups	O
.	O
</s>
<s>
In	O
large	O
organizations	O
,	O
this	O
is	O
a	O
task	O
usually	O
delegated	O
to	O
directory	O
services	O
,	O
such	O
as	O
openLDAP	B-Language
,	O
Novell	O
's	O
eDirectory	B-Application
or	O
Microsoft	O
's	O
Active	B-Protocol
Directory	I-Protocol
.	O
</s>
<s>
In	O
many	O
cases	O
,	O
the	O
directory	O
service	O
spans	O
many	O
file	B-Application
servers	I-Application
,	O
potentially	O
hundreds	O
for	O
large	O
organizations	O
.	O
</s>
