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Database snaphot

  • October 20, 2008 at 1:27 am

    #123952

    I found some articles says "If the data changes rapidly, the snapshot might run out of disk space." How this can happen, please explain!

    - Zahran -

  • October 20, 2008 at 2:03 am

    #886993

    The snapshot file is a sparse file. It may appear to be the same size as the source DB, but it's size on disk is typically a lot lower.

    When data is changed in the source DB, the old version of those pages must be copied over to the snapshot, if those pages aren't already there. Hence the size of the file on disk will grow, hence you can run out of disk space.

    Gail Shaw
    Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
    SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability

    We walk in the dark places no others will enter
    We stand on the bridge and no one may pass

  • October 23, 2008 at 6:22 pm

    #888969

    If you are planning to implement database snapshots, please go through the following link first.

    Looks like on some SAN \ disk array hardware combinations, there is a limitation on the size of database snapshot

    after which your main database would not allow anymore writes. Sounds weird right ... i got bitten by it few days back ...

    http://blogs.msdn.com/psssql/archive/2008/07/10/sql-server-reports-operating-system-error-1450-or-1452-or-665-retries.aspx

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