You surely have already seen those figures, a 15K disk does +/- 210 IOPS whilst SATA disk can barely achieve 30-40 IOPS.
How do they do to determine disks IOPS?
It is far from obvious and you must refer to the technical details provided by the disk manufacturer and use a simple formula given below. Also this is the theory, no file system, no data, no OS, this is raw disk power right off the pipe. Now let’s have a look at the formula:
1/(average latency in ms + average seek time for read or write in ms)
This is the specifications of a Seagate Cheetah 300GB 15K disk and actually have a look at the latency and seek times, that’s what we need for the formula.
So for this particular disk, theoretically the maximum we can expect is 1/(.0022)=454IOPS
And for the minimum, that I would call the best of the worst case, we can expect 1/(.006)=166IOPS
That gives us an average of 310IOPS! Not bad for the latest of Seagate’s high end disks family.
Now that you have the formula, go and check your own disk max/min/average IOPS and post it here 😉
Also read my other post on IOPS where I give the formula to calcuate the IOPS you can expect of a virtual environment.