<s>
In	O
storage	O
networking	O
,	O
”	O
persistent	B-Architecture
binding	I-Architecture
”	O
is	O
an	O
option	O
of	O
zoning	B-Architecture
.	O
</s>
<s>
Host-based	O
zoning	B-Architecture
is	O
usually	O
referred	O
to	O
as	O
persistent	B-Architecture
binding	I-Architecture
or	O
LUN	O
,	O
and	O
is	O
perhaps	O
the	O
least	O
implemented	O
form	O
of	O
zoning	B-Architecture
.	O
</s>
<s>
Because	O
it	O
requires	O
the	O
host	O
configuration	O
to	O
be	O
correct	O
in	O
order	O
to	O
avoid	O
zoning	B-Architecture
conflicts	O
,	O
this	O
form	O
of	O
zoning	B-Architecture
creates	O
a	O
greater	O
opportunity	O
for	O
administrative	O
errors	O
and	O
conflicting	O
access	O
to	O
targets	O
.	O
</s>
<s>
Moreover	O
,	O
zoning	B-Architecture
interfaces	O
vary	O
among	O
different	O
host	O
operating	B-General_Concept
systems	I-General_Concept
and	O
HBA	B-Architecture
's	O
—	O
increasing	O
the	O
possibility	O
for	O
administrative	O
errors	O
.	O
</s>
<s>
If	O
a	O
host	O
is	O
not	O
configured	O
with	O
the	O
zoning	B-Architecture
software	O
,	O
it	O
can	O
access	O
all	O
devices	O
in	O
the	O
fabric	O
and	O
create	O
an	O
even	O
higher	O
probability	O
of	O
data	O
corruption	O
.	O
</s>
<s>
Host-based	O
zoning	B-Architecture
is	O
often	O
used	O
when	O
clusters	O
are	O
implemented	O
to	O
control	O
the	O
mapping	O
of	O
devices	O
to	O
specific	O
target	O
IDs	O
.	O
</s>
<s>
However	O
,	O
it	O
should	O
never	O
be	O
the	O
only	O
form	O
of	O
zoning	B-Architecture
.	O
</s>
<s>
Augmenting	O
host-based	O
zoning	B-Architecture
with	O
storage	O
-	O
and	O
fabric-based	O
zoning	B-Architecture
is	O
the	O
only	O
acceptable	O
method	O
to	O
reliably	O
control	O
device	O
access	O
and	O
data	B-General_Concept
security	I-General_Concept
.	O
</s>
<s>
Basically	O
,	O
A	O
given	O
LUN	O
has	O
it	O
SCSI	B-Architecture
id	O
assigned	O
by	O
its	O
RAID	B-Device
device	I-Device
(	O
typically	O
a	O
SAN	O
)	O
.	O
</s>
<s>
But	O
for	O
some	O
purposes	O
it	O
's	O
useful	O
to	O
have	O
the	O
SCSI	B-Architecture
id	O
assigned	O
by	O
the	O
host	O
itself	O
:	O
that	O
's	O
persistent	B-Architecture
binding	I-Architecture
.	O
</s>
<s>
Without	O
persistent	B-Architecture
binding	I-Architecture
,	O
after	O
every	O
reboot	O
,	O
the	O
SCSI	B-Architecture
id	O
of	O
a	O
LUN	O
may	O
change	O
.	O
</s>
<s>
For	O
Example	O
,	O
under	O
Linux	B-Application
,	O
a	O
LUN	O
bound	O
on	O
/dev/sda	O
could	O
migrate	O
to	O
/dev/sdb	O
after	O
a	O
reboot	O
.	O
</s>
<s>
The	O
risks	O
augments	O
with	O
multipathing	B-General_Concept
.	O
</s>
<s>
Based	O
on	O
that	O
,	O
it	O
is	O
obvious	O
that	O
many	O
software	O
may	O
crash	O
without	O
persistent	B-Architecture
binding	I-Architecture
.	O
</s>
<s>
Operating	B-General_Concept
systems	I-General_Concept
and	O
upper-level	O
applications	O
(	O
such	O
as	O
backup	O
software	O
)	O
typically	O
require	O
a	O
static	O
or	O
predictable	O
SCSI	B-Architecture
target	O
ID	O
for	O
their	O
storage	O
reliability	O
and	O
persistent	B-Architecture
binding	I-Architecture
affords	O
that	O
happening	O
.	O
</s>
<s>
That	O
's	O
zoning	B-Architecture
.	O
</s>
<s>
The	O
zone	O
is	O
usually	O
set	O
on	O
the	O
central	O
point	O
of	O
connection	O
of	O
the	O
hosts	O
and	O
the	O
DISK	O
ARRAY	O
:	O
the	O
FC	B-Architecture
switch	I-Architecture
.	O
</s>
<s>
Zoning	B-Architecture
is	O
sometimes	O
confused	O
with	O
LUN	B-Architecture
masking	I-Architecture
,	O
because	O
it	O
serves	O
the	O
same	O
goals	O
.	O
</s>
<s>
LUN	B-Architecture
masking	I-Architecture
,	O
however	O
,	O
works	O
on	O
Fibre	O
channel	O
level	O
4	O
(	O
i.e.	O
</s>
<s>
on	O
SCSI	B-Architecture
level	O
)	O
,	O
while	O
zoning	B-Architecture
works	O
on	O
level	O
2	O
.	O
</s>
<s>
This	O
allows	O
zoning	B-Architecture
to	O
be	O
implemented	O
on	O
switches	O
,	O
whereas	O
LUN	B-Architecture
masking	I-Architecture
is	O
performed	O
on	O
endpoint	O
devices	O
-	O
host	B-Architecture
adapters	I-Architecture
or	O
disk	B-Device
array	I-Device
controllers	I-Device
.	O
</s>
<s>
Some	O
fibre	B-Architecture
channel	I-Architecture
switches	I-Architecture
allow	O
zoning	B-Architecture
at	O
the	O
LUN	O
level	O
,	O
effectively	O
implementing	O
LUN	B-Architecture
masking	I-Architecture
at	O
the	O
switch	O
.	O
</s>
<s>
This	O
form	O
of	O
zoning	B-Architecture
has	O
to	O
be	O
augmented	O
by	O
another	O
zoning	B-Architecture
:	O
RAID	B-Architecture
ARRAY	I-Architecture
based	O
or	O
fabric-based(FC switch )	O
to	O
improve	O
security	O
and	O
avoid	O
any	O
errors	O
.	O
</s>
