Method for Allocating Spare Sectors After SAT
Original Publication Date: 1986-Jun-01
Included in the Prior Art Database: 2005-Mar-09
A surface-analysis test (SAT) at time of manufacture of disk drives determines which sectors are defective. In this method, spare sectors are allocated uniformly so that subsequently grown defective sectors will be near a spare and the push-down will be short. As nonuniformities in spares develop during the life of a disk drive, a utility program can be run to redistribute the spares. Allocating spares uniformly is illustrated by the following example. The number of sectors per track in the example is much less than for a real file. Example specifications: . 14 sectors per track . 4 tracks per cylinder . 2 defects per cylinder (average SAT defect rate) . 1 spare per track after SAT . 7 maximum length of defect list. Information derived from the specifications and assumptions: . 56 physical sectors per cylinder .