Tuesday, 14 July 2009

Affinity & Affinity I/O - Some notes

Processor Affinity settings bind SQL Server activity to specific processors
If you are unlucky enough to be sharing a server with another application, this would be where to prevent  SQL using all CPUs.

By default, the affinity settings are 'automatic' i.e. use all processors.


Affinity mask (Processor Affinity) - Controls processors as this can be degrative to performance.

Affinity I/O mask (I/O Affinity) - controls server I/O (you nominate processors to be used for i/o activity)

Never mark the same processors for affinity mask and affinity i/o mask. (see Technet link for details)

Update 10/10/2010 :
Because changing I/O Affinity requires a restart of the SQL Server Service, The radio buttons 'Configured values' and 'Running values' at the bottom of the Affinity screen will show differences in configuration until the restart occurs.

Technet : Affinity Mask Option

John Daskalakis : SQL Server 2008 and Processors

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