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  1. #1
    Join Date
    Dec 2002
    Posts
    45

    Unanswered: additional data files not filing

    We have a quad sql server that runs OLTP transactions at the rate of
    100's per second (read & Write).

    We used to have all the tables on 1 file but started to notice high contention on this file. We added 3 more files to match the processor number. The problem is that the 3 additional files are not filling with data. Does anyone know why this happens or can reccommend a fix?
    --
    will

  2. #2
    Join Date
    Dec 2002
    Posts
    1,245
    Verify that the newly added files are in the appropriate file group (probably PRIMARY) and are of the appropriate file type (ie, they were created as data files, not log files). Also, your new file(s) may not get data written to them if the old file still has space available.

    Your logic for reducing contention by adding files to match the number of processors does not make sense. Contention is caused by physical IO going to the same physical disk and getting backed up because the pipe to the physical disk is too small. You would add files to a database filegroup to ease contention by creating the files on separate physical disks. It has no relation the number of CPUs.

    Regards,

    hmscott
    Have you hugged your backup today?

  3. #3
    Join Date
    Dec 2002
    Posts
    45
    Yes they are all the same file type (data files).

    Microsoft claims that you should have a seperate file per processor for high contention OLTP sql servers. Parallelism is the goal here. Sql server can only access 1 file per cpu at any one time. If it was a dual processor machine It would have less impact considering the OS & tempdb usually have something going on in parallel.

    Considering we have a quad sql server = 4 files per file group.

    As an FYI we are running a raid 10 with 14 disks.

  4. #4
    Join Date
    Dec 2002
    Posts
    1,245
    Hmm, not doubting you, but could you send a link with the MS info? I had not seen that before.

    As for your issue, what's the state of the original data file? Full, nearly full or not even close? Also, can you verify that the new files you added were updateable (ie, not read-only)? Beyond that, I would try testing some scenarios out on a development server somewhere.

    Regards,

    hmscott
    Have you hugged your backup today?

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