HP Cisco MDS 9216 - Fabric Switch Configuration Manual page 1020

Configuring iSCSI
S e n d d o c u m e n t a t i o n c o m m e n t s t o m d s f e e d b a c k - d o c @ c i s c o . c o m
Cut-through mode improves the read operation performance over store-and-forward mode. The port
on the IPS module or MPS 14/2 module achieves this by forwarding each Fibre Channel data-in
frame to the iSCSI host as it is received without waiting for the whole exchange complete. There is
no difference for write data-out operations from store-and-forward mode.
Figure 50-29
Figure 50-29
Pass -Thru
iSCSI initiator
Command1
iSCSI Data-
in PDU #1,
DSlen = 1KB
iSCSI
Data-in
PDU #2
iSCSI
Data-in
PDU #16
Response1
Command2
Table 50-1
Cisco MDS 9000 Family CLI Configuration Guide
50-34
compares the messages exchanged by the iSCSI routing modes.
iSCSI Routing Modes
MDS FC Target
Command
Data1
Data2
Data16
Status
compares the advantages and disadvantages of the different iSCSI routing modes.
Store -Forward
iSCSI initiator MDS FC Target
Command1
Command
Data1
Wait for all
Data to
arrive
Data16
TCP part 1
contains iSCSI
Data-in PDU #1
DSlen = 16KB
TCP part 2
TCP part 16
Status
Response1
Command2
Chapter 50 Configuring iSCSI
Cut -Thru
iSCSI initiator MDS
Command1
TCP part 1
contains iSCSI
Data-in PDU #1
Data frame is
DSlen = 16KB
forwarded as
it is received
TCP part 2
TCP part 16
Response1
Command2
OL-16184-01, Cisco MDS SAN-OS Release 3.x
FC Targ
Command
Data1
Data2
Data16
Status