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  1. #1
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    Unanswered: SQL Server Cluster on Clariion SAN

    Is there a recommendation or best practice concerning the placement of SQL executable binaries (e.g. sqlserver.exe) in a clustered configuration on a SAN?

    In other words, am I required to put the binaries on a local hard drive, or is it permissible to install SQL into a clustered environment and specify a drive volume that is on the SAN?

    Many thanks for your response,

    hmscott

  2. #2
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    There is no need for program files to be on the clustered storage, leave them on local drives.

  3. #3
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    With a Symetrix SAN, you definitely want to have the OS and critical application files on local disk. I've heard that the Clariion is not as sensitive to this, but I'd still be cautious.

    -PatP

  4. #4
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    This is actually a recommendation of not Clarion SAN only (we use Clarion and EMC). By putting program files on SAN you defeat the purpose of clustering by introducing one point of failure.

  5. #5
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    Originally posted by rdjabarov
    This is actually a recommendation of not Clarion SAN only (we use Clarion and EMC). By putting program files on SAN you defeat the purpose of clustering by introducing one point of failure.
    You Also increase the contention for i/o controller even though its fibre channel. We have one setup where the exe's are on the local scsi, the transaction logs on a RAID 1 device, and the datafiles on the SAN. Albeit a bit more complicated, its seems to run well.

    I have not found much in the way of performance tuning with SANs, most docs I have read regard it as a black hole, with the data being striped over several disks, you clearly can't assign filegroups to spindles.

    Does anyone know of white paper or other on good practices with a SAN?

    And what about defragging a SAN? Any tools used in production.

    Regards,
    Rob.

  6. #6
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    You are correct, in that when dealing with a SAN, the rules do change. Writes occur at the speed of fibre. Predictable reads (the ones that the SAN pre-fetches) also occur at the speed of fibre. Spindles are meaningless.

    This causes all kinds of rules about databases and their disks to become irrelevant. Separate spindles for logs are meaningless, they just don't matter. Defragging actually hurts performance measurably, because it changes the read patterns. If you want a disk to respond faster, make it bigger (!!!), because that adds more spindles which buys you a larger share of cache. All of the hard won knowledge that you've built up about hardware just goes out the window.

    Another side issue, is that this makes the PC bus become your weak link. Faster front side busses make more difference than faster CPU. Sometimes they even make more difference than more RAM.

    -PatP

  7. #7
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    Disk latency was significantly lower and never became an issue on the large-scale environment due to increased I/O performance provided by the SAN.

    Couple of articles referring SAN information:
    http://www.sql-server-performance.com/ew_san.asp
    http://www1.us.dell.com/content/topi...555&l=en&s=biz from DELL.


    HTH
    Originally posted by jimskit
    You Also increase the contention for i/o controller even though its fibre channel. We have one setup where the exe's are on the local scsi, the transaction logs on a RAID 1 device, and the datafiles on the SAN. Albeit a bit more complicated, its seems to run well.

    I have not found much in the way of performance tuning with SANs, most docs I have read regard it as a black hole, with the data being striped over several disks, you clearly can't assign filegroups to spindles.

    Does anyone know of white paper or other on good practices with a SAN?

    And what about defragging a SAN? Any tools used in production.

    Regards,
    Rob.
    --Satya SKJ
    Microsoft SQL Server MVP
    [IMG]http://sqlserver-qa.net/google_bart.gif[/IMG]

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