FUJITSU MHW2060AC - Manual (Page 251)

6.3 Defect Processing
(3) Automatic alternating processing
This technology assigns a defective sector to a spare sector of a spare cylinder for
alternate assignment.
This device performs automatic alternating processing in the event of any of the
following errors.
• Automatic alternating processing is attempted for read error recovery by
reaching the specified retry cycle while a read error retry is in progress.
Before attempting automatic alternating processing, writing and reading of
already corrected data is repeated for the sector in which an error occurred. If
a read error does not occur during this reading operation, automatic
alternating processing is not performed.
• If error recovery is not successful even if a write fault error retry is executed,
automatic alternating processing is performed.
Figure 6.6 shows an example where automatic alternating processing is applied to
sector (physical) 5 with cylinder 0 and head 0.
Sector (physical)
Cylinder 0
Head 0
Defec-
tive
sector
(Not used)
Alternate cylinder 0
Head 0
This is assigned to an unassigned sector.
Already
assigned
779 780
779 780
Notes:
1. The alternate cylinder is assigned to an inner cylinder in each zone.
2. When an access request for sector 5 is issued, the sector assigned for
alternating processing of the alternate cylinder must be accessed instead of
physical sector 5.
If an access request for sectors after sector 5 is issued, seek is executed to
cylinder 0, head 0 in order to continue processing.
Figure 6.6 Automatic alternating processing
C141-E258 6-11