Table of Contents
Advertisement
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 .
Figure 35-13
Figure 35-13 iSCSI Routing Modes
Pass -Thru
iSCSI initiator
MDS
FC Target
Command1
Command
iSCSI Data-
in PDU #1,
Data1
DSlen = 1KB
iSCSI
Data2
Data-in
PDU #2
iSCSI
Data16
Data-in
PDU #16
Status
Response1
Command2
Table 35-1
Table 35-1 Comparison of iSCSI Routing Modes
Mode
Pass-thru
Store-and-forward
Cut-thru
Cisco MDS 9000 Family Configuration Guide
35-28
compares the messages exchanged by the iSCSI routing modes.
Store -Forward
iSCSI initiator
MDS
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
compares the advantages and dissuasiveness of the different iSCSI routing modes.
Advantages
Low-latency
Data digest can be used
Higher data transfer
performance
Improved read performance
over store-and-forward
FC Target
iSCSI initiator
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
Disadvantages
Lower data transfer performance.
Data digest cannot be used.
If Fibre Channel target sent read data for
different commands interchangeably, data of the
first one will be forwarded in cut-thru mode but
data of subsequent commands will be buffered
and the behavior will be the same as
store-and-forward mode.
Data digest cannot be used.
Chapter 35
Configuring iSCSI
Cut -Thru
MDS
FC Target
Command
Data1
Data2
Data16
Status
OL-6973-03, Cisco MDS SAN-OS Release 2.x
Advertisement
Table of Contents
