FUJITSU MHK2090AT - Manual (Page 202)

6.4 Defect Management
C141-E088-03EN 6-13
(2) Alternate cylinder assignment
A defective sector is assigned to the spare sector in the alternate cylinder.
This processing is performed when the alternate assignment is specified in the
FORMAT TRACK command or when the automatic alternate processing is
performed at read error occurrence.
Figure 6.8 shows an example where (physical) sector 5 is detective on head 0 in
cylinder 0.
Notes:
1) 4 alternate cylinders are provided for each head in zone 14 (inner
side).
2) When an access request to physical sector 5 is specified, the device
accesses the alternated sector in the alternate cylinder instead of
sector 5. When an access request to sectors next to sector 5 is
specified, the device seeks to cylinder 0, head 0, and continues the
processing.
Figure 6.8 Alternate cylinder assignment
(3) Automatic alternate assignment
The device performs the automatic alternate assignment when ECC correction
performance is increased during read error retry, a read error is recovered. Before
automatic alternate assignment, the device performs rewriting the corrected data to
the erred sector and rereading. If no error occurs at rereading, the automatic
alternate assignment is not performed.
506 505
506 505 7 6 4 3 2 1