Filegroup on the SAN...

  • We store our filegroups on the SAN.  I have been reading that to improve performance, put indexes in their own filegroup on another disk, and large tables in their own as well.  I am uncertain that this statement is true with the SAN.  Is there anyone that can shed some light this for me?

    Thanks!

  • The problem with splitting data that way is that it assumes that the workload is evenly distributed across the files.  It is rare to actually have accurate information about that, and even if you do, it can change at different times of the day or over time.

    I distribute the workload by creating multiple files in a filegroup, and placing one file on each disk.  Since the data is more or less evenly distributed across all disks, it tends to balance the IO evenly across all disks without having to spend a lot of time analyzing usage of individual tables or indexes.

     

  • maybe this can help a bit ...

    http://www.sql-server-performance.com/ew_san.asp 

    Johan

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  • It creates more administration and complicates disaster recovery, but it can help. However it's not necessarily a big performance boost:

    http://blogs.msdn.com/psssql/archive/2007/02/21/sql-server-urban-legends-discussed.aspx

  • great article ALZDBA ... I wish there was more information on ...

     

    Of course there are other factors, such as RAID stripe size, RAID controller CPU utilization, controller caches, data file placement, etc., but they are beyond the scope of this article.

    The reason is that we went into all of those areas when configuring our SAN ... a sanity check primer woould have been nice.

    RegardsRudy KomacsarSenior Database Administrator"Ave Caesar! - Morituri te salutamus."

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