6.4 Read-Ahead Cache
Index
Sector (Physical)
Cylinder 0
Head 0
Alternate cylinder
Head 0
0 | 1 | 2 | 3 | 4 |
| 5 | 6 |
| 658 | 659 |
|
|
|
| Defective |
|
|
|
|
|
|
|
|
|
| sector |
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
0 | 1 | 2 | 3 | (unused)4 | 5 | 6 |
| 658 | 659 | |
Sector (Logical)
Already assigned
Defective sector is assigned to unassigned sector.
Notes:
1)4 alternate cylinders are provided for each head in zone 14 (inner side).
2)When an access request to logical sector 4 is specified, the device accesses the alternated sector in the alternate cylinder instead of sector 4. When an access request to sectors next to logical sector 5 is specified, the device seeks to cylinder 0, head 0, and continues the processing.
Figure 6.6 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.
An unrecoverable write error occurs during write error retry, automatic alternate assignment is performed.
6.4 Read-Ahead Cache
After read command which involves read data from the disk medium is completed, the
