Advantages in Multiple Files per Filegroup per Spindle ?

  • In some of the databases I'm taking over ( in the 1.5 TB range ) I'm finding multiple files per filegroup on same spindle. Not dealing with table partitioning across multiple file groups etc.

    Is there any advantage to multiple files per filegroup versus a single file ?

    Some DBMSs this can trigger more IO threads, and other parallel operations but I'm not clear on all the implications in SQLServer.

    Obviously lots of unknowns in this question but what are the tradeoffs generally ?

  • No advantages. It doesn't allow more IO threads (all threads in SQL can issue IOs to any file), it doesn't spread out IO load. As long as you're talking just a few files, no disadvantage either. When it gets to a few hundred files there can be a performance impact in some cases.

    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
  • to add to Gail, in fact in some cases if you have a large number of files per filegroup the file switching can be a performance issue. SQL Server attempts to stripe when multiple files are implemented per filegroup, this has to be monitored and calculated ongoing so that sql server knows exactly how full a particular file is.

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    "Ya can't make an omelette without breaking just a few eggs" 😉

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