HP A7533A - Brocade 4Gb SAN Switch Base, Administrator'S Manual

Page: 304 / 576

302 iSCSI gateway service
At the iSCSI gateway port, the incoming iSCSI data is converted to FCP (SCSI on FC) by the iSCSI virtual
initiator, and then forwarded to the FC target. This allows low-cost servers to leverage an existing FC
infrastructure.
To represent all iSCSI initiators and sessions, each iSCSI portal has one iSCSI virtual initiator (VI) to the FC
fabric that appears as an N_Port device with a special WWN format. Regardless of the number of iSCSI
initiators or iSCSI sessions sharing the portal, Fabric OS uses one iSCSI VI per iSCSI portal.
Figure 34 shows the interaction of different layers from the iSCSI initiator stack to the FC target stack,
including the iSCSI gateway service used during protocol translation.
Figure 34 iSCSI-to-FC translation
Basic vs. advanced LUN mapping
Fabric OS provides the following two methods to map physical FC targets (LUNs) to iSCSI virtual targets
(VTs):
• ” Basic LUN mapping ”
• ” Advanced LUN mapping ”
Basic LUN mapping
Fabric OS provides a mechanism that maps LUNs to iSCSI VTs, a one-to-one mapping with unique iSCSI
Qualified Names (IQNs) for each target. It presents an iSCSI VT for each native FC target to the IP network
and an iSCSI VI for each iSCSI port to the FC fabric.
The following figure shows a basic LUN mapping scenario for an FC target with four LUNs.
Figure 35 iSCSI VT basic LUN mapping
Advanced LUN mapping
SCSI VTs can be mapped to more than one physical FC target, and the LUNs can be mapped to different
virtual LUNs. Figure 36 shows an advanced mapping scenario.
iS C S I gateway s ervic e
S torage
(device s erver)
S C S I
F C P
F C
F C target
Application
S C S I
iS C S I
T C P /IP
iS C S I initiator
F C P (F C -4)
F C (F C -2/F C -3)
iS C S I
T C P /IP
iS C S I virtual
initiator (V I)
iS C S I virtual
target (V T )
40. 3
iS C S I virtual target (V T )
2
3
0
1
LUN
F C target
2
3
0
1
LUN
40. 9