Hyperthreading info for SQL and Citrix

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Rodney R. Fournier [MVP] - 22 Nov 2005 16:13 GMT

Just got this email from someone in Ops:

http://news.zdnet.co.uk/0,39020330,39237341,00.htm

http://blogs.msdn.com/slavao/archive/2005/11/12/492119.aspx

Synopsis - Hyperthreading (Intel specific technology) can seriously impedes
performance in SQL and Citrix especially under heavy load.

Is this correct? Any ideas from the SQL peanut gallery here? We only run SQL
clusters, 25-30 of them all on at least dual Xeon's with Hyperthreading.

Cheers,

Rod

MVP - Windows Server - Clustering
http://www.nw-america.com - Clustering Website
http://msmvps.com/clustering - Blog
http://www.clusterhelp.com - Cluster Training

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Andrew J. Kelly - 22 Nov 2005 16:46 GMT

There is no way to make an accurate blanket statement that HT helps or hurts
performance. I have certainly seen it do both depending on the type of
workload. The only way to know for sure is to do extensive testing in your
exact environment with it on and then again with it off.

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Andrew J. Kelly SQL MVP

> Just got this email from someone in Ops:
>
[quoted text clipped - 17 lines]
> http://msmvps.com/clustering - Blog
> http://www.clusterhelp.com - Cluster Training

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Uttam Parui[MS] - 30 Nov 2005 22:49 GMT

I agree with Andrew. The only way to tell if Hyperthreading is good in your environment is do testing. It may be good for
some environments and may not be good for others.

There is a nice blog from Slava Oks on hyperthreading that you may find useful

Be aware: To Hyper or not to Hyper
http://blogs.msdn.com/slavao/archive/2005/11/12/492119.aspx

HTH,

Best Regards,

Uttam Parui
Microsoft Corporation

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