SQL Server Performance

Formulas to Calculate RAID Performance?

Discussion in 'Performance Tuning for Hardware Configurations' started by DBADave, Sep 22, 2003.

  1. DBADave New Member

    What formula exist to calculate RAID performance? I would like to compare RAID 0+1, 5 and 10. I know the forumla deals with I/O per second, but I don't recall its syntax.

    Thanks, Dave
  2. Luis Martin Moderator

  3. gaurav_bindlish New Member

    The book Microsoft® SQL Server 2000™ Performance Tuning Technical Reference @http://www.microsoft.com/mspress/books/4944.asp has excellent discussion on this topic.

    Gaurav
    Moderator
    Man thrives, oddly enough, only in the presence of a challenging environment- L. Ron Hubbard
  4. Muhammed New Member

  5. ykchakri New Member

    RAID 0:

    I/Os per Disk = (Reads + Writes) / Number of Disks

    RAID 1:

    I/Os per Disk = [Reads + (2*Writes)]/2

    RAID 5:

    I/Os per Disk = [Reads + (4*Writes)] / Number of Disks

    RAID 10:

    I/Os per Disk = [Reads + (2 * Writes)] / Number of Disks

  6. DBADave New Member

    That's exactly what I was looking for. How did you find this information?

    Thanks, Dave
  7. joechang New Member

    in raid 1 or 10, 1 logical write requires 2 physical disk writes
    in raid 5, 1 logical write require 1 physical read of the data block, 1 read for the parity, 1 write for the data, 1 write for the parity for a total of 4 I/Os
  8. DBADave New Member

    Thanks for the help.

    Dave
  9. Tango New Member

    Hi ykchakri and all!

    I'm joining this thread late, since I'm new to the forum and just read about it...
    In the RAID 10 formula, by "number of disks" do you mean physical or logical disks? That is, if I have a 4 disks RAID 10 array, do I have to count 4 (for the physical disks), or just 2 (for the 2 mirrors that build the RAID 10 volume)?

    Thanks.


    quote:Originally posted by ykchakri

    RAID 0:

    I/Os per Disk = (Reads + Writes) / Number of Disks

    RAID 1:

    I/Os per Disk = [Reads + (2*Writes)]/2

    RAID 5:

    I/Os per Disk = [Reads + (4*Writes)] / Number of Disks

    RAID 10:

    I/Os per Disk = [Reads + (2 * Writes)] / Number of Disks


  10. joechang New Member

    the formulas apply to actual physical disks, not the physical disks in Windows Disk Management.

    Suppose you have a HW RAID controller, Use the Windows physical disk counters (MS seems to suggest the logical counters are expensive to maintain)

    the performance counters the Operating System reports is for the logical drive presented by the RAID controller.
    So, if the OS reports 100 reads and 100 writes from a RAID 10 logical drive,

    the IO going to the actual physical drives is: 100 for the reads, and 200 for the 100 writes (100 for each part of the mirrored set)
  11. Twan New Member

    Also remember that the stripe size for RAID is significantly smaller for RAID 5 then other forms of RAID, making the read/write performance even worse

    Cheers
    Twan
  12. Mitya New Member

    and what about RAID15? how is the perfomance calculated?
  13. Luis Martin Moderator

    Mitya, welcome to the forums.
    Please start a new thread. This one is 9 years old.:)

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