2 Iron

Windows 2012 R2 and 10Gb iSCSI

Has anyone changed the either of the two settigs below on Windows 2012 R2 to improve iSCSI performance?

I have seen it mentioned in various places outside of EMC but I don't see it as an EMC best practice.

My customer has disabled the Chimney one and seen much improved performance in testing with Intel 10Gb.

Would welcome comments.

netsh int tcp set global chimney=disabled

netsh int tcp set global rss=disabled

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4 Replies

Re: Windows 2012 R2 and 10Gb iSCSI

Hi Smarti,

I think the below mentioned  kb might be helpful.




1 Nickel

Re: Windows 2012 R2 and 10Gb iSCSI


There's no information about TCP Chimney/RSS in the EMC VNX iSCSI best practices at the moment. However, they have been mentioned in other articles such as these two:

https://support.emc.com/kb/83708 : Slow reads and writes to CIFS shares when copying many small files.

https://support.emc.com/kb/163358 : How to disable IPV6, TCP Chimney and Receive Side Scaling (RSS) on Windows 2008 (This is a NetWorker KB article, not VNX).

I'd say, if you're experiencing a performance-related problem, follow the recommendations and disable these options.

If the problem persists however, open up a Service Request while referencing this Microsoft KB (http://support.microsoft.com/kb/951037). The performance support team will research any bottlenecks on the VNX, and advise you accordingly.

I hope this helps,


2 Iron

Re: Windows 2012 R2 and 10Gb iSCSI

Yeah, I knew about delayed ack. But that wasn't the issue. The other two were the problem and when we disabled them we got much better performance.

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4 Ruthenium

Re: Windows 2012 R2 and 10Gb iSCSI

As mentioned previously EMC does not have any recommendations for configuration settings on server NICs using iSCSI. We've heard that in some cases, disabling the off-load functions on some TOE NIC's (older Broadcom TOE NICs for example) can help performance but we don't do any performance testing of server NIC's for iSCSI, we relay on what is supported on the OS from the OS vendor.


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