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March 6th, 2013 14:00

Windows "File Allocation Unit Size" and SQL Server 2008

Hello,

I am trying to obtain confirmation about using a 64kb file allocation unit size for SQL data and log volumes presented from a VMAX. 

According to the TechBook "Microsoft SQL Server on EMC Symmetrix Storage Systems"  "...partition alignment and the resulting volume alignment should not be confused with the Windows Allocation Unit size specified when formatting the volume.  These are two different processes."  "A number of EMC best practice documents exist on this matter and are available on Powerlink.  These documents discuss the issue, and describe the processes to implement corrective measures."  (page 415 - SQL Server layout recommendations)

http://www.emc.com/collateral/software/solution-overview/h2203-ms-sql-svr-symm-ldv.pdf

I have not been able to locate the documents on Powerlink.

We have an application and the vendor is suggesting 64kb file allocation units for SQL Server.  The storage team is taking the position that the default 4kb file size is what EMC recommends.  The EMC documentation is vague.

Please help.

Thanks.

9 Legend

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20.4K Posts

March 6th, 2013 15:00

David, you might get more feedback if you post your question in "Everything Microsoft at EMC" section of the forum.

March 6th, 2013 16:00

Thank you.  How do I do that?

Also, in case anyone else finds this thread, I found this...

SQL Server Storage Design Best Practice

I think it answers my question, but it is marked as "Assumed Answered"

9 Legend

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20.4K Posts

March 6th, 2013 18:00

2 Intern

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467 Posts

March 6th, 2013 19:00

Not directly related to SQL,  but when doing stress testing with Exchange on a vmax the allocation unit size made a huge different in response time doing from 4k to 64k.  At 4k we had an average response time of nearly 200ms peek during stress test.  After changing it to 64k it peeked at 45ms during heavy io testing

790 Posts

March 7th, 2013 09:00

Your question has been moved to the Symmetrix support forum, where it has a better chance of being seen and answered

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