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Determining IOPS in performance monitor

Maquinaloca asked
Last Modified: 2013-11-14
I am in the process of purchasing a new san and I am trying to calculate my disk i/o requirments. On my current san I captured perfmon logs for about three days now I am trying to determine which counters I need to review to determine the total iops.

Also how do I calculate the %read vs %writes.
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The counters that show you IOPS are: Physical Disk Writes/sec and Physical Disk Reads/sec. You need to determine the maximum that all the hosts will be hitting the SAN with and size according to that number. You also need to do some additional calculations depending on which RAID type you intend to use. For random workloads (Exchange, SQL, virtualisation platforms):

 If you're using RAID 5:

Total disk IOPS = read IOPS + (write IOPS x 4).

If you're using RAID 1/0:

Total disk IOPS = read IOPS + (write IOPS x 2).

Determine the number of disks by dividing total IOPS by 200 for 15K rpm FC drives, 140 for 10K rpm FC or SAS drives and 80 for SATA drives. The king-of-the-IOPS-kids are flash drives where you can achieve 3000 IOPS per drive, but they are still reasonably expensive for enterprise-level kit. You can get some cheap and cheerful arrays that use personal storage flash drives, but I'd be very careful checking write performance before laying down the company's hard-earned. Typically, if you get the performance right, space and bandwidth (MB/sec) take care of themselves, although you'll need to worry about bandwidth if you're planning workloads such as media serving etc.


I read some other articles that listed Disk Transfers/sec as the counter that gives you the IOPS the host is generating.
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