Changing the default allocation Unit size

[DBAWinnipeg]

Hardware Vendor recommended reformatting the data drives (hosted in a SAN)and changing the default allocation Unit (4kb) to 64kb. I am not sure if there is any benefit to be gained here and the client wants me to confirm if this has been done. I was wondering if anyone has been to a site where SQL Server data drive is formatted with bigger allocation units. If so,did it improve I/O performance? I do not seem to find any documentation in support of this, but would welcome one if anyone has.

Thanks in advance!!!

Colin in da 'Peg

 

[NathanGriffiths]

From BOL 'File Systems'

When running on Windows NT, SQL Server performance can be improved further if the databases are created on disks formatted using NTFS and, specifically, 64-KB extent sizes. In Windows 2000, setting the file system cluster size to 64-KB extent size using the /A format option will also improve performance. For more information about formatting an NTFS disk, see the Windows NT or Windows 2000 documentation.

I've never had to format format 64Kb extents myself though, but I imagine heavily loaded systems would see the most performance improvement.

Nathan

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