<s>
In	O
computer	B-Architecture
hardware	I-Architecture
,	O
a	O
host	B-Architecture
controller	I-Architecture
,	O
host	B-Architecture
adapter	I-Architecture
,	O
or	O
host	B-Architecture
bus	I-Architecture
adapter	I-Architecture
(	O
HBA	O
)	O
,	O
connects	O
a	O
computer	O
system	B-Architecture
bus	I-Architecture
,	O
which	O
acts	O
as	O
the	O
host	O
system	O
,	O
to	O
other	O
network	B-Architecture
and	O
storage	B-General_Concept
devices	O
.	O
</s>
<s>
The	O
terms	O
are	O
primarily	O
used	O
to	O
refer	O
to	O
devices	O
for	O
connecting	O
SCSI	B-Architecture
,	O
SAS	O
,	O
Fibre	B-Architecture
Channel	I-Architecture
and	O
SATA	O
devices	O
.	O
</s>
<s>
Devices	O
for	O
connecting	O
to	O
FireWire	B-Protocol
,	O
USB	B-Protocol
and	O
other	O
devices	O
may	O
also	O
be	O
called	O
host	B-Architecture
controllers	I-Architecture
or	O
host	B-Architecture
adapters	I-Architecture
.	O
</s>
<s>
Host	B-Architecture
adapters	I-Architecture
can	O
be	O
integrated	O
in	O
the	O
motherboard	O
or	O
be	O
on	O
a	O
separate	O
expansion	B-Device
card	I-Device
.	O
</s>
<s>
The	O
term	O
network	B-Protocol
interface	I-Protocol
controller	I-Protocol
(	O
NIC	O
)	O
is	O
more	O
often	O
used	O
for	O
devices	O
connecting	O
to	O
computer	B-Architecture
networks	I-Architecture
,	O
while	O
the	O
term	O
converged	B-Protocol
network	I-Protocol
adapter	I-Protocol
can	O
be	O
applied	O
when	O
protocols	O
such	O
as	O
iSCSI	B-Protocol
or	O
Fibre	B-Protocol
Channel	I-Protocol
over	I-Protocol
Ethernet	I-Protocol
allow	O
storage	B-General_Concept
and	O
network	B-Architecture
functionality	O
over	O
the	O
same	O
physical	O
connection	O
.	O
</s>
<s>
A	O
connects	O
a	O
host	O
system	O
and	O
a	O
peripheral	O
SCSI	B-Architecture
device	O
or	O
storage	B-General_Concept
system	I-General_Concept
.	O
</s>
<s>
Typically	O
a	O
device	B-Application
driver	I-Application
,	O
linked	O
to	O
the	O
operating	B-General_Concept
system	I-General_Concept
,	O
controls	O
the	O
host	B-Architecture
adapter	I-Architecture
itself	O
.	O
</s>
<s>
In	O
a	O
typical	O
parallel	O
SCSI	B-Architecture
subsystem	O
,	O
each	O
device	O
has	O
assigned	O
to	O
it	O
a	O
unique	O
numerical	O
ID	O
.	O
</s>
<s>
As	O
a	O
rule	O
,	O
the	O
host	B-Architecture
adapter	I-Architecture
appears	O
as	O
SCSI	B-Architecture
ID	O
7	O
,	O
which	O
gives	O
it	O
the	O
highest	O
priority	O
on	O
the	O
SCSI	B-Architecture
bus	O
(	O
priority	O
descends	O
as	O
the	O
SCSI	B-Architecture
ID	O
descends	O
;	O
on	O
a	O
16-bit	B-Device
or	O
"	O
wide	O
"	O
bus	O
,	O
ID	O
8	O
has	O
the	O
lowest	O
priority	O
,	O
a	O
feature	O
that	O
maintains	O
compatibility	O
with	O
the	O
priority	O
scheme	O
of	O
the	O
8-bit	O
or	O
"	O
narrow	O
"	O
bus	O
)	O
.	O
</s>
<s>
The	O
host	B-Architecture
adapter	I-Architecture
usually	O
assumes	O
the	O
role	O
of	O
SCSI	B-Device
initiator	I-Device
,	O
in	O
that	O
it	O
issues	O
commands	O
to	O
other	O
SCSI	B-Architecture
devices	O
.	O
</s>
<s>
A	O
computer	O
can	O
contain	O
more	O
than	O
one	O
host	B-Architecture
adapter	I-Architecture
,	O
which	O
can	O
greatly	O
increase	O
the	O
number	O
of	O
SCSI	B-Architecture
devices	O
available	O
.	O
</s>
<s>
Major	O
SCSI	B-Architecture
adapter	O
manufacturers	O
are	O
HP	O
,	O
ATTO	O
Technology	O
,	O
Promise	O
Technology	O
,	O
Adaptec	O
,	O
and	O
LSI	O
Corporation	O
.	O
</s>
<s>
LSI	O
,	O
Adaptec	O
,	O
and	O
ATTO	O
offer	O
PCIe	O
SCSI	B-Architecture
adapters	O
which	O
fit	O
in	O
Apple	O
Mac	O
,	O
on	O
Intel	O
PCs	B-Device
,	O
and	O
low-profile	O
motherboards	O
which	O
lack	O
SCSI	B-Architecture
support	O
due	O
to	O
the	O
inclusion	O
of	O
SAS	O
and/or	O
SATA	O
connectivity	O
.	O
</s>
<s>
The	O
term	O
host	B-Architecture
bus	I-Architecture
adapter	I-Architecture
(	O
HBA	O
)	O
may	O
be	O
used	O
to	O
refer	O
to	O
a	O
Fibre	B-Architecture
Channel	I-Architecture
interface	O
card	O
.	O
</s>
<s>
In	O
this	O
case	O
,	O
it	O
allows	O
devices	O
in	O
a	O
Fibre	B-Architecture
Channel	I-Architecture
storage	B-General_Concept
area	O
network	B-Architecture
to	O
communicate	O
data	O
between	O
each	O
otherit	O
may	O
connect	O
a	O
server	O
to	O
a	O
switch	O
or	O
storage	B-General_Concept
device	O
,	O
connect	O
multiple	O
storage	B-General_Concept
systems	I-General_Concept
,	O
or	O
connect	O
multiple	O
servers	O
.	O
</s>
<s>
Fibre	B-Architecture
Channel	I-Architecture
HBAs	O
are	O
available	O
for	O
open	B-Operating_System
systems	I-Operating_System
,	O
computer	O
architectures	O
,	O
and	O
buses	O
,	O
including	O
PCI	B-Protocol
and	O
SBus	B-Architecture
(	O
obsolete	O
today	O
)	O
.	O
</s>
<s>
Each	O
Fibre	B-Architecture
Channel	I-Architecture
HBA	O
has	O
a	O
unique	O
World	O
Wide	O
Name	O
(	O
WWN	O
)	O
,	O
which	O
is	O
similar	O
to	O
an	O
Ethernet	O
MAC	O
address	O
in	O
that	O
it	O
uses	O
an	O
OUI	O
assigned	O
by	O
the	O
IEEE	O
.	O
</s>
<s>
There	O
are	O
two	O
types	O
of	O
WWNs	O
on	O
a	O
HBA	O
;	O
a	O
node	O
WWN	O
(	O
WWNN	O
)	O
,	O
which	O
is	O
shared	O
by	O
all	O
ports	O
on	O
a	O
host	B-Architecture
bus	I-Architecture
adapter	I-Architecture
,	O
and	O
a	O
port	O
WWN	O
(	O
WWPN	O
)	O
,	O
which	O
is	O
unique	O
to	O
each	O
port	O
.	O
</s>
<s>
The	O
major	O
Fibre	B-Architecture
Channel	I-Architecture
HBA	O
manufacturers	O
are	O
QLogic	O
and	O
Broadcom	O
.	O
</s>
<s>
HBA	O
is	O
also	O
known	O
to	O
be	O
interpreted	O
as	O
High	O
Bandwidth	O
Adapter	O
in	O
cases	O
of	O
Fibre	B-Architecture
Channel	I-Architecture
controllers	O
.	O
</s>
<s>
The	O
term	O
(	O
HCA	O
)	O
is	O
usually	O
used	O
to	O
describe	O
InfiniBand	B-Architecture
interface	O
cards	O
.	O
</s>
<s>
ATA	O
host	B-Architecture
adapters	I-Architecture
are	O
integrated	O
into	O
motherboards	O
of	O
most	O
modern	O
PCs	B-Device
.	O
</s>
<s>
They	O
are	O
often	O
improperly	O
called	O
disk	B-General_Concept
controllers	I-General_Concept
.	O
</s>
<s>
The	O
correct	O
term	O
for	O
the	O
component	O
that	O
allows	O
a	O
computer	O
to	O
talk	O
to	O
a	O
peripheral	O
bus	O
is	O
host	B-Architecture
adapter	I-Architecture
.	O
</s>
<s>
A	O
proper	O
disk	B-General_Concept
controller	I-General_Concept
only	O
allows	O
a	O
disk	O
to	O
talk	O
to	O
the	O
same	O
bus	O
.	O
</s>
<s>
SAS	O
or	O
serial-attached	O
SCSI	B-Architecture
is	O
the	O
current	O
connectivity	O
to	O
replace	O
the	O
previous	O
generation	O
parallel-attached	O
SCSI	B-Architecture
(	O
PAS	O
)	O
devices	O
.	O
</s>
<s>
Ultra320	O
was	O
the	O
highest	O
level	O
of	O
parallel	O
SCSI	B-Architecture
available	O
,	O
but	O
SAS	O
has	O
since	O
replaced	O
it	O
as	O
the	O
highest-performing	O
SCSI	B-Architecture
technology	O
.	O
</s>
<s>
External	O
Serial	O
ATA	O
(	O
eSATA	O
)	O
disk	B-Device
enclosures	I-Device
and	O
drives	O
are	O
available	O
in	O
the	O
consumer	O
computing	O
market	O
,	O
but	O
not	O
all	O
SATA-compatible	O
motherboards	O
and	O
disk	B-General_Concept
controllers	I-General_Concept
include	O
eSATA	O
ports	O
.	O
</s>
<s>
In	O
the	O
mainframe	B-Architecture
field	O
,	O
the	O
terms	O
host	B-Architecture
adapter	I-Architecture
or	O
host	B-Architecture
bus	I-Architecture
adapter	I-Architecture
were	O
traditionally	O
not	O
used	O
.	O
</s>
<s>
A	O
similar	O
goal	O
was	O
achieved	O
since	O
the	O
1960s	O
with	O
channel	O
I/O	O
,	O
a	O
separate	O
processor	O
that	O
can	O
access	O
main	O
memory	O
independently	O
,	O
in	O
parallel	O
with	O
CPU	O
(	O
like	O
later	O
DMA	B-General_Concept
in	O
personal	B-Device
computer	I-Device
field	O
)	O
,	O
and	O
that	O
executes	O
its	O
own	O
I/O	O
-dedicated	O
programs	O
when	O
pointed	O
to	O
such	O
by	O
the	O
controlling	O
CPU	O
.	O
</s>
<s>
Protocols	O
used	O
by	O
channel	O
I/O	O
to	O
communicate	O
with	O
peripheral	B-Device
devices	I-Device
include	O
ESCON	B-Device
and	O
newer	O
FICON	B-Architecture
.	O
</s>
