DISK ZONING

9/20/2008

Disk Zoning takes advantage of the fact that the outer tracks on a disk are longer than the inner tracks. They can, all other things being equal, hold more data. Floppy disks are not zoned. Neither were early hard drives. This led to the development of disk software that assumes a fixed number of sectors per track.

With the advent of large, sophisticated ROMs on disk units, it became feasible to translate the simplistic fixed number of sectors used by external software into a more complex data layout used on the actual disk. One of the features of the complex data layout is the division of the disk into a number of zones with increasingly more sectors per zone on the longer outer tracks. Modern hard drives may have two dozen zones.

Since hard drives operate at a fixed rotation speed, not only do the outer zones hold more data, but they transfer data at a greater rate. This can significantly affect disk benchmarking since data written to different zones can alter overall performance. There is no external indication of how many zones there are, or of how many sectors are in any given zone.