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
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Cisco MDS 9000 Family CLI Configuration Guide
OL-16184-01, Cisco MDS SAN-OS Release 3.x
Chapter 42 Configuring iSCSI
Configuring iSCSI
Figure 42-13
compares the messages exchanged by the iSCSI routing modes.
Figure 42-13
iSCSI Routing Modes
Table 42-1
compares the advantages and disadvantages of the different iSCSI routing modes.
Data1
Data2
iSCSI Data-
in PDU #1,
DSlen = 1KB
Data16
Status
iSCSI
Data-in
PDU #16
Command1
Command
Response1
Command2
Data1
Data16
Status
TCP part 16
Command1
Command
Response1
Command2
Data1
Data16
Status
TCP part 16
Command1
Command
Response1
Command2
TCP part 2
Pass -Thru
Store -Forward
Cut -Thru
iSCSI initiator
MDS
FC Target
iSCSI initiator
MDS
FC Target
iSCSI initiator
MDS
FC Targ
TCP part 1
contains iSCSI
Data-in PDU #1
DSlen = 16KB
Wait for all
Data to
arrive
TCP part 2
Data2
Data frame is
forwarded as
it is received
130687
iSCSI
Data-in
PDU #2
TCP part 1
contains iSCSI
Data-in PDU #1
DSlen = 16KB
Table 42-1
Comparison of iSCSI Routing Modes
Mode
Advantages
Disadvantages
Pass-thru
Low-latency
Data digest can be used
Lower data transfer performance.
Store-and-forward
Higher data transfer
performance
Data digest cannot be used.
Cut-thru
Improved read performance
over store-and-forward
If the Fibre Channel target sent read data for
different commands interchangeably, data of the
first command is forwarded in cut-thru mode but
the data of subsequent commands is buffered
and the behavior is the same as
store-and-forward mode.
Data digest cannot be used.