Lab Setup; Configuring From The Bottom Switch Using The Cli - Cisco 9134 - MDS Multilayer Fabric Switch Troubleshooting Manual

iSCSI TCP Performance Issues
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
Any value starting with 64K (> 65535 = 0xFFFF bytes) will automatically trigger TCP window scaling
according to RFC 1323. The IPS TCP window scaling begins only when the remote peer (iSCSI client
in this case) requests it. This means that you need to configure the TCP stack of your client to trigger
this functionality (see
For the Fibre Channel side, depending on the direction of the traffic, the BB_credit of the ports
corresponding to the input interfaces (sending/receiving traffic to/from the iSCSI side) could be
increased, especially in the case of local Gigabit Ethernet attached iSCSI clients.

Lab Setup

This is the lab setup that was used in collecting the performance-related information.
•
•
•
•
•

Configuring from the Bottom Switch Using the CLI

The following example is the configuration for the 9216 switch shown in
iscsi initiator name iqn.1987-05.com.cisco:02.75af2f95624c.shark-nas
pWWN 20:05:00:0c:30:6c:24:42
vsan 777
vsan 778
iscsi virtual-target name shark_nas
pWWN 50:05:07:63:00:c8:94:4c fc-lun 0000 iscsi-lun 0000 secondary-pwwn
50:05:07:63:00:c4:94:4c
pWWN 50:05:07:63:00:c8:94:4c fc-lun 0001 iscsi-lun 0001 secondary-pwwn
50:05:07:63:00:c4:94:4c
initiator iqn.1987-05.com.cisco:02.75af2f95624c.shark-nas permit
interface GigabitEthernet2/1
ip address 10.48.69.251 255.255.255.192
iscsi authentication none
no shutdown
vrrp 1
priority 110
address 10.48.69.250
(This is the iSCSI target IP address for the Windows iSCSI client.)
no shutdown
interface iscsi2/1
tcp pmtu-enable
tcp window-size 1024
(To increase the receive window size of the IPS module (in kilobytes).)
tcp sack-enable
Cisco MDS 9000 Family Troubleshooting Guide, Release 3.x
20-50
Figure 20-13).
The server was an IBM Pentium III server: Dual CPU @ 1.13 GHz.
The TCP window size at both ends was set to 1MB (1024K).
The IBM ESS Shark had a hardcoded BB_credit value of 64 (not configurable).
The fcrxbbcredit on the corresponding switch port (fc1/3) was set to the same value.
The C4 and C8 represented the corresponding port WWNs (pWWN) for the IBM Shark storage
subsystem. The full pWWN is as follows:
C4 50:05:07:63:00:c4:94:4c (in VSAN 778)
–
C8 50:05:07:63:00:c8:94:4c (in VSAN 777)
–
Chapter 20 Troubleshooting IP Storage Services
Figure 20-13.
OL-9285-05