Calculating IOPS?

[mbrownnyc]

Hello,

I'm looking for a reliable formula to calculate IOPS of disk subsystems.

I found the following on expert-exchange. Can anyone verify it as correct?

Single Disk IOPS = 1 / Average Latency, where
Average Latency = Rotational Latency + Average Seek Latency
Rotational Latency =
        14.3 ms @ 4200 RPM
        11.1 ms @ 5400 RPM
        8.3 ms @ 7200 RPM
        6.0 ms @ 10K RPM and
        4.0 ms @ 15K RPM
Average Seek Latency = Varies with Manufacturer, typically
        Notebook drives ~ 12+ ms
        7.2K SATA drives ~ 8 to 10 ms
        10K SATA drives ~ 4.5 to 5.0 ms
        10/15K SAS drives ~ 3 to 4 ms

RAID Read IOPS = Sum of all Single Disk IOPS
RAID Write IOPS
        RAID0 = Sum of all Single Disk IOPS
        RAID1/10 = Half of the sum of all Single Disk IOPS
        RAID5* = One-quarter the sum of all Single Disk IOPS
        RAID6* = One-sixth the sum of all Single Disk IOPS

* Note while there is an XOR calculation involved with RAID5/6, it's usually inconsequential in modern hardware.

If it is incorrect, can someone provide a reliable formula to calculate IOPS?

I am attempting to compare IO for several disk solutions... looking to keep costs low (ruling out fibre-channel, etc). Looking at RAID10 versus 15k drives, etc.


Thanks for your time,

Matt