<s>
Direct-attached	B-General_Concept
storage	I-General_Concept
(	O
DAS	O
)	O
is	O
digital	B-General_Concept
storage	I-General_Concept
directly	O
attached	O
to	O
the	O
computer	O
accessing	O
it	O
,	O
as	O
opposed	O
to	O
storage	O
accessed	O
over	O
a	O
computer	O
network	O
(	O
i.e.	O
</s>
<s>
network-attached	B-Application
storage	I-Application
)	O
.	O
</s>
<s>
DAS	O
consists	O
of	O
one	O
or	O
more	O
storage	O
units	O
such	O
as	O
hard	B-Device
drives	I-Device
,	O
solid-state	B-Device
drives	I-Device
,	O
optical	O
disc	O
drives	O
within	O
an	O
external	B-Device
enclosure	I-Device
.	O
</s>
<s>
The	O
term	O
"	O
DAS	O
"	O
is	O
a	O
retronym	O
to	O
contrast	O
with	O
storage	O
area	O
network	O
(	O
SAN	O
)	O
and	O
network-attached	B-Application
storage	I-Application
(	O
NAS	B-Application
)	O
.	O
</s>
<s>
A	O
typical	O
DAS	O
system	O
is	O
made	O
of	O
a	O
data	B-General_Concept
storage	I-General_Concept
device	I-General_Concept
(	O
for	O
example	O
enclosures	O
holding	O
a	O
number	O
of	O
hard	B-Device
disk	I-Device
drives	I-Device
)	O
connected	O
directly	O
to	O
a	O
computer	O
through	O
a	O
host	B-Architecture
bus	I-Architecture
adapter	I-Architecture
(	O
HBA	O
)	O
.	O
</s>
<s>
The	O
main	O
protocols	O
used	O
for	O
DAS	O
connections	O
are	O
ATA	B-Protocol
,	O
SATA	O
,	O
eSATA	O
,	O
NVMe	B-Application
,	O
SCSI	B-Architecture
,	O
SAS	O
,	O
USB	B-Protocol
,	O
USB	B-Protocol
3.0	O
and	O
IEEE	B-Protocol
1394	I-Protocol
.	O
</s>
<s>
Most	O
functions	O
found	O
in	O
modern	O
storage	O
do	O
not	O
depend	O
on	O
whether	O
the	O
storage	O
is	O
attached	O
directly	O
to	O
servers	O
(	O
DAS	O
)	O
,	O
or	O
via	O
a	O
network	O
(	O
SAN	O
and	O
NAS	B-Application
)	O
.	O
</s>
<s>
In	O
enterprise	O
environments	O
,	O
direct-attached	B-General_Concept
storage	I-General_Concept
systems	O
can	O
utilize	O
storage	O
devices	O
that	O
have	O
higher	O
endurance	O
in	O
terms	O
of	O
data	O
workload	O
capability	O
,	O
along	O
with	O
scalability	O
in	O
the	O
amount	O
of	O
capacity	O
that	O
storage	O
arrays	O
can	O
achieve	O
compared	O
to	O
NAS	B-Application
and	O
other	O
consumer-graded	O
storage	O
devices	O
.	O
</s>
<s>
The	O
key	O
difference	O
between	O
DAS	O
and	O
NAS	B-Application
is	O
that	O
DAS	O
storage	O
does	O
not	O
incorporate	O
any	O
network	O
hardware	O
and	O
related	O
operating	O
environment	O
to	O
provide	O
a	O
facility	O
to	O
share	O
storage	O
resources	O
independently	O
of	O
the	O
host	O
so	O
is	O
only	O
available	O
via	O
the	O
host	O
to	O
which	O
the	O
DAS	O
is	O
attached	O
.	O
</s>
<s>
DAS	O
is	O
typically	O
considered	O
much	O
faster	O
than	O
NAS	B-Application
due	O
to	O
lower	O
latency	O
in	O
the	O
type	O
of	O
host	O
connection	O
although	O
contemporary	O
network	O
and	O
direct	O
connection	O
throughput	O
typically	O
exceeds	O
the	O
raw	O
read/write	O
performance	O
of	O
the	O
storage	O
units	O
themselves	O
.	O
</s>
<s>
A	O
SAN	O
(	O
storage	O
area	O
network	O
)	O
has	O
more	O
in	O
common	O
with	O
a	O
DAS	O
than	O
a	O
NAS	B-Application
with	O
the	O
key	O
difference	O
being	O
that	O
DAS	O
is	O
a	O
1:1	O
relationship	O
between	O
storage	O
and	O
host	O
whereas	O
SAN	O
is	O
many	O
to	O
many	O
.	O
</s>
