Let’s face it – disks are slow. In the last decade almost nothing has happened to those nice little zinc-oxide platters that have been spinning in our data centers. For example, 15K rpm disks came out a lllloooonnnggg time ago and still represent the leading edge of the rotational speed of the disks. Unfortunately, while there have been considerable improvements in the areal density through techniques such as perpendicular recording, it is the rotational speed that defines how many I/O operations per second (IOPS) a disk can handle. Seagate and other disk manufacturers generally use formulas such as:

IOPS = 1000/(seek time + rotational latency)

where

rotational latency = ((1/(RPM/60))/2)*1000

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