<s>
Serial	B-Architecture
Storage	I-Architecture
Architecture	I-Architecture
(	O
SSA	O
)	O
was	O
a	O
serial	O
transport	O
protocol	O
used	O
to	O
attach	O
disk	B-Device
drives	I-Device
to	O
server	B-Application
computers	I-Application
.	O
</s>
<s>
IBM	O
produced	O
a	O
number	O
of	O
successful	O
products	O
based	O
upon	O
this	O
standard	O
before	O
it	O
was	O
overtaken	O
by	O
the	O
more	O
widely	O
adopted	O
Fibre	B-Architecture
Channel	I-Architecture
protocol	O
.	O
</s>
<s>
SSA	O
was	O
promoted	O
as	O
an	O
open	O
standard	O
by	O
the	O
SSA	O
Industry	O
Association	O
,	O
unlike	O
its	O
predecessor	O
the	O
first	O
generation	O
Serial	O
Disk	B-Device
Subsystem	O
.	O
</s>
<s>
It	O
was	O
also	O
adopted	O
as	O
an	O
American	O
National	O
Standards	O
Institute	O
(	O
ANSI	O
)	O
X3T10.1	O
standard	O
.	O
</s>
<s>
SSA	O
devices	O
are	O
logically	O
SCSI	B-Architecture
devices	O
and	O
conform	O
to	O
all	O
of	O
the	O
SCSI	B-Architecture
command	O
protocols	O
.	O
</s>
<s>
Up	O
to	O
192	O
hot	B-Device
swappable	I-Device
hard	O
disk	B-Device
drives	I-Device
can	O
be	O
supported	O
per	O
system	O
.	O
</s>
<s>
Up	O
to	O
32	O
separate	O
RAID	B-Architecture
arrays	I-Architecture
can	O
be	O
supported	O
per	O
adaptor	O
,	O
and	O
arrays	O
can	O
be	O
mirrored	O
across	O
servers	O
to	O
provide	O
cost-effective	O
protection	O
for	O
critical	O
applications	O
.	O
</s>
<s>
SSA	O
was	O
deployed	O
in	O
server	O
RAID	B-Architecture
environments	O
,	O
where	O
it	O
was	O
capable	O
of	O
providing	O
for	O
up	O
to	O
80	O
Mbyte/s	O
of	O
data	O
throughput	O
,	O
with	O
sustained	O
data	O
rates	O
as	O
high	O
as	O
60	O
Mbytes/s	O
in	O
non-RAID	O
mode	O
and	O
35	O
Mbytes/s	O
in	O
RAID	B-Architecture
mode	O
.	O
</s>
<s>
The	O
copper	O
cables	O
used	O
in	O
SSA	O
configurations	O
are	O
round	O
bundles	O
of	O
two	O
or	O
four	O
twisted	O
pairs	O
,	O
up	O
to	O
25	O
metres	O
long	O
and	O
terminated	O
with	O
9-pin	O
micro-D	B-Protocol
connectors	O
.	O
</s>
<s>
For	O
longer-distance	O
connections	O
,	O
it	O
is	O
possible	O
to	O
use	O
fiber-optic	B-Architecture
cables	I-Architecture
up	O
to	O
10km	O
(	O
6	O
mi	O
)	O
in	O
length	O
.	O
</s>
<s>
Signals	O
are	O
differential	B-General_Concept
TTL	I-General_Concept
.	O
</s>
<s>
The	O
transport	O
layer	O
protocol	O
is	O
non-return-to-zero	B-Protocol
,	O
with	O
8B/10B	B-Protocol
encoding	I-Protocol
(	O
10	O
bits	O
per	O
character	O
)	O
.	O
</s>
<s>
Higher	O
protocol	O
layers	O
were	O
based	O
on	O
the	O
SCSI-3	O
standard	O
.	O
</s>
