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  1. #1
    Join Date
    Oct 2006
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    115

    Question Unanswered: SQL Server 2005/2008 file I/O pattern

    Anybody knows if SQL server is writing the disk in sequential or in random manner?

    What if the SQL server is being hosted in a virtualized environment? Would it have any difference in terms of file I/O pattern to the physical disk?

  2. #2
    Join Date
    Dec 2007
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    There is no simple answer to your question. It's not really a SQL Server question at all because it depends on factors like the type of storage subsystem, RAID level, number of spindles, etc.

    At the OS level log operations are always sequential. Whether data file operations are as well is highly dependent on the type of workload.

  3. #3
    Join Date
    Feb 2004
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    Provided Answers: 54
    Quote Originally Posted by tingshen
    Anybody knows if SQL server is writing the disk in sequential or in random manner?
    Yes.
    Quote Originally Posted by tingshen
    Would it have any difference in terms of file I/O pattern to the physical disk?
    No.

    -PatP

  4. #4
    Join Date
    Oct 2006
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    115
    Quote Originally Posted by dportas
    There is no simple answer to your question. It's not really a SQL Server question at all because it depends on factors like the type of storage subsystem, RAID level, number of spindles, etc.

    At the OS level log operations are always sequential. Whether data file operations are as well is highly dependent on the type of workload.
    uhm...............
    Last edited by tingshen; 04-04-09 at 11:48.

  5. #5
    Join Date
    Dec 2007
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    Quote Originally Posted by tingshen
    uhm...............
    Do you still have a question? You'll need to give us more explanation if you want more specific answers than you've already had.

  6. #6
    Join Date
    Oct 2006
    Posts
    115
    Alright, let me tell you my problem in details.

    We are going to use Intel Modular Server for virtualization purpose. It has an integrated SAN storage and we are considering using SSDs. The windows servers to be virtualized are mostly SQL server 2008.

    Why is there a concern of sequential or random write? For SSD, read is not much issue, it's just too fast compared to traditional HDD, even SAS can't smell the smoke. However, at the moment, there are 2 types of SSDs optimized for different kind of operation. 1 is good for sequential write, wheres Intel is optimized for random write.

    therefore, understanding the file I/O pattern will help us in choosing the type of SSDs as our SAN storage media.

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