File Allocation Unit Size and Partition Alignment

  • There is of course another dimension to consider after you have created your LUNs and exposed them to your

    SQL Box, which is the Partition alignment and File Allocation Unit (Cluster) size to be used in formatting the drive.

    Have a look at the following documentation on SQL Server 2008, and SQL for some insight:

    A Cluster size of 64KB is normally fine for use with SQL Server.

  • Remember Windows 2008 does partition alignment for you 😉

  • Since we are talking about the 'right' things to do for your SAN disks on SQL Server let us not forget to check with you specific SAN manufacturer's best practices/whitepapers as well. Their unique information combined with Microsoft's can create one screaming SAN. LUN sizes, number of disks, SAN stripe or block sizes all contribute to this and usually are specific to the SAN manufacturer. Oh, let us not forget the technical specs on your HBAs as well ... maximum queue depth, read/write buffering and percentage of read/write activity all by drive letter (system DBs, application DB data, application DB log and tempdb) !

    RegardsRudy KomacsarSenior Database Administrator"Ave Caesar! - Morituri te salutamus."

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