Enterprise storage vendors like to talk in terms of input/outputs per second (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. Database applications are often complicated mixes of I/O with caching involved—sequential reads, seeks, and commits all compete—rather than always being seek-bound.
Spindle is often used as a synonym for a single disk drive, and is used interchangeably here that way. It's ...
