Random access and I/Os Per Second

Enterprise storage vendors like to talk in terms of Input/Outputs Per Second or IOPS. If you're buying a SAN for example, expect to be asked "how many IOPS do you expect in total and per spindle?" and for measurements provided by the vendor proving good performance to be in this unit. This number represents typical disk performance on a seek-heavy workload, and unfortunately it is a poor one to fixate on for database applications. Databases are often complicated mixes of I/O with caching involved—sequential reads, seeks, and commits all compete—rather than always being seek-bound.

Note

Spindle is often used as a synonym for a single disk drive, and is used interchangeably here that way. It's more correctly used to only refer to a single section of a disk, the part that rotates. In this case common use trumps correctness for most writing about this subject.

It's straightforward to compute IOPS for a single disk...