Alternate Cylinder Assignment - Fujitsu MPE3XXXAE Product Manual

(2)

Alternate cylinder assignment

A defective sector is assigned to the spare sector in the alternate cylinder.
This processing is performed when a physical track contains three or more defective sectors,
and when the automatic alternate processing is performed.
Figure 6.8 shows an example where (physical) sector 5 is detective on head 0 in cylinder 0.
Index
Sector (physical)
1 2
Cylinder 0
Head 0
1 2
Sector (logical)
Alternate
cylinder
Head 0
Defective sector is assigned to unassigned sector.
4 alternate cylinders are provided for each head in zone 13 (inner side).
1 alternate cylinder is provided in outer side.
When an access request to 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.
(3) Automatic alternate assignment
The device performs the automatic assignment at following case.
1) Automatic alternate assignment is done when a read error is recovered by retry beyond the
regulation number of times during read error retry.
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.
And, this automatic alternate assignment is done only once toward the read command
receipt from the host.
2) When a write error occurs and the error does not recovered.
6 - 12
3 4 5 6
Defective
sector
3 4 6
(unused)
Already
assigned
Figure 6.8 Alternate cylinder assignment
C141-E093-01EN
7
7
576
575
299 300
575 576
298 299
299 300