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RAID1 or RAID5 performance expections

Answered RAID1 or RAID5 performance expections

  • Saturday, January 05, 2013 5:51 PM
     
     
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    Hi

    We running a more or less small DWH with round about 100Gbyte. Because of new integration we will have a new expected size of 1-2Tbyte.

    The actual simple setup have an throughput of 150Mbyte/s (sorry, do not know the exact configuration). What is a common expectation on HD throughput with Raid5 data and Raid1 log? Seems the best solution for this scenario because of the better read performance of Raid5.

    What do you think about a HD setup of four 4x1TB Raid 5 and 2x500Gbyte Raid 1 for this setup?

    Thanks for some hints,

    Cheers

     

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  • Monday, January 07, 2013 7:45 AM
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    Hi Chris,

    RAID 1: Disk mirroring, the data is written redundantly to pairs of drives and can be read independently from each drive. 
    RAID 5 : Disk striping with parity, the data is written evenly across multiple drives and includes redundant parity data.

    If we let SQL Server strip the data to multiple drives, we still need to protect those drives from disk failure. The way to do that is to make sure that the data files are written to the logical drives of a RAID 1 array. This way, a single disk failure will not affect the stability of SQL Server.

    Please refer to the details:
    http://support.microsoft.com/kb/857894
    http://blogs.msdn.com/b/teamcenteronsql/archive/2010/04/27/raid-1-0-and-sql-server.aspx

    Thanks,
    Eileen

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    Eileen Zhao
    TechNet Community Support

     
  • Monday, January 07, 2013 9:32 AM
     
     
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    Hi. Thanks for the links, but I am looking for an expectation for the speed. What is common for a well configured SQL Server. Like 500Mbyte/s or somethink like this to get a feeling if the hardware works propably. Thanks Nils
     
  • Thursday, January 10, 2013 6:03 AM
     
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    It all depends on the types of the HDD you have, types of HDD array, etc.

    Also, usage patterns are important - proportion between number of writes and reads.

    Very simplified:

    - max read speed is the speed of RAID1: single drive multiplied by number of drives (unless HDD controller has big cache), RAID5: single drive multiplied by (number of drives - 1)

    - write: RAID1 half of read speed / 2, RAID5 - it depends on the controller.

    RAID5 is good only when you need to save on numbers of drives, it gives more capacity.

    If you need more throughput, buy more drives, add smarter controller or use solid state cache.