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iSCSI target is OpenSolaris 2009.6 (COMSTAR)

iSCSI traffic is in the separate VLAN, the target and all initiators use 9k jumbo frames, jumbo are enabled on switch.

iSCSI initiator on RHEL5 shows nice performance around 80mb/sec read, 80mb/sec write (copying the regular files/using dd, then doing sync, then calculating actual speed)

The problem is with the iSCSI initiator on Windows XP - very slow, can't get more than 20-25mb/sec. Network card: Intel 82574L, TCP offload is on.

Any suggestions?

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I'm assuming you mean Megabytes/sec there not Megabits/sec.

Check that you've unbound the standard Windows Networking protocols from the iSCSI network for a start, just in case they are causing unwanted additional traffic. Check that you are using the most up to date iSCSI initiator from Microsoft, that Jumbo frames are set to 9k, disable Windows Indexing on that drive if it's enabled, likewise AV if you're testing performance. Check that you're not seeing any errors on the iSCSI NIC or on the Switch.

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Here's a link telling how to optimize TCP/IP stack for iSCSI and run initial tests to check network performance (should do wire speed for TCP):

It's on StarWind forum but it's all the same for all of the targets and Windows initiators.


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