This article copy from http://blogs.microsoft.co.il/blogs/yuval14/archive/2011/07/15/how-to-improve-iscsi-performance.aspx
If you want to know more detail, please go the above link to see.
The following post cover a few tips and tricks that can improve you iSCSI performance.
General
1. Use the latest Microsoft operating System.
2. Update the current ISCSI initiator to the latest version.
3. If it applicable, use a HBA (Host Bus Adapter) with iSCSI accelerator.
4. In some scenarios, you may need to use the latest DSM (Device-Specific Module) software module, that can be obtained from the storage/HBA vendor.
5. ISCSI usually supported in 1 GB or higher infrastructure. Using 10/100 MB infrastructure can lead to low performance/data corruption.
6. Please use a dedicated network adapter/s (or HBA) for iSCSI connection. Combining regular network traffic and iSCSI traffic can lead to performance and security issues.
7. The network switch/s that planed to be used for the iSCSI infrastructure should be certificate for ISCSI traffic.
Note: Not all the common network switches officially support iSCSI.
9. Use the latest driver for the network adapter/HBA card/s.
10. For backup LUN by using direct SAN technology, its recommended to allow the backup server to have a Read only privilege to the required LUN.
11. Although iSCSI support block level transfer over TCP/IP, a regular network issues can lead to performance issues. To avoid performance issues, its recommended to implemented a full network design that includes redundant and optimize Spanning Tree Protocol (STP) implementation.
12. Consider to use Jumbo frame on the iSCSI network (Its specially recommended to environments that planed to be use for large file transfer).
Network Performance
1. Review the current network settings by using the command:
netsh interface tcp show global
2. Consider to optimize the autotuninglevel level by implement one of the following settings:
netsh interface tcp set global autotuninglevel=disabled
3. Consider to disable Chimney Offload State support:
netsh int tcp set global chimney=disabled
4. Consider to disable Receive Side Scaling (RSS) support:
netsh int tcp set global rss=disabled
5. Although its usually supported, don’t use any firewall/routing device in the ISCSI network.
6. Consider to disable EnableICMPRedirect support:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters
Value DWORD 32bits: EnableICMPRedirect set to "0"
7. To implement a high availably and high performance solution, consider to implement MPIO (Microsoft® Multipath I/O):
Understanding MPIO Features and Components
8. Integrating iSCSI, FCIP, and iFCP technologies required a special care. For start, please review: Mr. Jane Shurtleff article:
IP storage: A review of iSCSI, FCIP, iFCP
Note3:Its recommended to reboot the server after applying this changes.
