Cisco MDS 9000 Series Troubleshooting Manual page 146

Fine Tuning/Troubleshooting IPS iSCSI TCP Performance
S e n d 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 .
Verify that the local port, rather than a remote that is reached via an ISL link
is used for the storage target by the above field to avoid suboptimal access to storage.
You can see that C8 is the locally attached port of the shark storage subsystem.
MDS_BOTTOM#
Thefollowing example shows the effect of changing the Gigabit MTU on FC RcvDataFieldSize.
interface GigabitEthernet2/1
ip address 10.48.69.249 255.255.255.192
iscsi authentication none
switchport mtu 2440
no shutdown
vrrp 1
address 10.48.69.250
no shutdown
MDS_Top# show iscsi remote-node iscsi-session-detail tcp-parameters
iSCSI Node name is iqn.1987-05.com.cisco:02.75af2f95624c.shark-nas
iSCSI alias name: SHARK-NAS
Node WWN is 20:00:00:0c:30:6c:24:42 (dynamic)
Member of vsans: 777, 778
Number of Virtual n_ports: 1
Virtual Port WWN is 20:00:00:0c:30:6c:24:42 (configured)
Cisco MDS 9000 Family Troubleshooting Guide
5-52
pWWN: 50:05:07:63:00:c8:94:4c
nWWN: 50:05:07:63:00:c8:94:4c
Session state: LOGGED_IN
1 iSCSI sessions share this FC session
Target: shark_nas
Negotiated parameters
RcvDataFieldSize 2048 our_RcvDataFieldSize 1392
MaxBurstSize 0, EMPD: FALSE
Random Relative Offset: FALSE, Sequence-in-order: Yes
Statistics:
PDU: Command: 0, Response: 1612007
Interface iSCSI 2/1, Portal group tag is 0x1001
VSAN ID 0, FCID 0x
No. of FC sessions: 1
No. of iSCSI sessions: 1
iSCSI session details
Target node:
Statistics:
PDU: Command: 0, Response: 0
Bytes: TX: 0, RX: 0
Number of connection: 1
TCP parameters
Local 10.48.69.250:3260, Remote 10.48.69.233:1026
Path MTU: 2440 bytes
Retransmission timeout: 420 ms
Round trip time: Smoothed 94 ms, Variance: 83
Advertized window: Current: 999 KB, Maximum: 1000 KB, Scale: 4
Peer receive window: Current: 1024 KB, Maximum: 1024 KB, Scale: 4
Congestion window: Current: 11 KB
VSAN ID 777, FCID 0x700003
No. of FC sessions: 1
No. of iSCSI sessions: 1
iSCSI session details
Target node: shark_nas
0
Chapter 5 Troubleshooting IP Storage Issues
OL-5183-02, Cisco MDS SAN-OS Release 1.3