"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...

On some drives, rather than a stored defect map, defective sectors
are
'jumped' over via a linkage table built right into the individual
sector
headers. Those sorts MUST be formatted in a way to reflect the bad
spots
on the medium.

LLoyd

This describes the process:
http://www-947.ibm.com/support/entry...id=mcgn-3n3k7b

Initially bad sectors are recorded in the P-List and skipped as the
sectors are sequentially numbered. Bad sectors that appear after the
sector addresses have been written go into the G-list so that a seek
to them is redirected to a spare sector located elsewhere, which slows
down disk access time. The operating system can also link bad sectors
into a dummy file.
jsw