allocation unit size and performance ..

  • Hi all ,

    I have done some SQL reading and noticed that most SQL servers, by default, have hard drives formatted with 4K allocation unit size instead of recommended 64K . We checked some of our latest SQL build and the hard drives, formatted for the SQL database, have the default allocation unit size 4K or 8 K instead of recommended 64K. I think allocation unit size is one of factors to look at while investigating a degraded performance of SQL server. I read that significant performance gains may be obtained by sizing this to a larger value in order to reduce disk I/Os; however, the default value is based on the size of the physical disk. The best practice for SQL Server is to choose 64 KB because this reduces the likelihood of I/Os that span distinct NTFS allocations, which then might result in split I/Os.

    Can any one have tried out these options and did you get ant significant results?.

    All suggestions are greatly appreciated.

    Elias

  • This was removed by the editor as SPAM

  • I'd go with with 8k or 64k, but have not tested enough to know for sure what the performance gain would be.

    Andy

    http://www.sqlservercentral.com/columnists/awarren/

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