Storage & Capacity

• dhechle

  SSC Eights!

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  July 6, 2009 at 9:41 am

  #131778

  We are looking at purchasing a SAN therefore i am beginning to gather some stats to help with the storage/capacity planning.

  I am currently using perfmon to retrieve disk reads/sec and disk writes/sec to discover how many IOPS our database server is doing.

  However I have read in text books and on the web that to work out the current ops per disk depending on RAID levels I would need to use the following formulas:

  RAID 1:

  operations per disk = (reads + (2 * writes)) / 2

  RAID 10:

  operations per disk = (reads + (2 * writes)) / number of disks

  A sample of data at a certain time from one of our drives that is a RAID 10 of 4 disks is:

  disk read/sec = 2939 and disk write/sec = 480

  So to find the IOPS placed on each disk at that time would i simply do:

  (2939 + (2 * 480) / 4

  = 975 IOPS

  And then to figure out how many disks i ideally need given they do roughly 180 IOPS would i use the following formula:

  (2939 + (2 * 480) /180

  = 22 disks

  I would appreciate any feedback, comments on this to point me in the right direction.

  Thanks in advance