Spare Area; Alternating Defective Sectors - Fujitsu MHA2021AT Product Manual

Operations

6.4.1 Spare area

Following two types of spare area are provided for every physical head.
1) Spare cylinder for sector slip:
used for alternating defective sectors at formatting in shipment (4 cylinders)
2) Spare cylinder for alternative assignment:
used for automatic alternative assignment at read error occurrence.
(2 cylinders)

6.4.2 Alternating defective sectors

The two alternating methods described below are available:
(1) Sector slip processing
A defective sector is not used and is skipped and a logical sector address is
assigned to the subsequent normal sector (physically adjacent sector to the
defective sector).
When defective sector is present, the sector slip processing is performed in the
formatting.
Figure 6.7 shows an example where (physical) sector 5 is defective on head 0 in
cylinder 0.
1 2
0 1
If an access request to physical sector 5 is specified, the device accesses physical sector 6 instead of sector 5.
6-12
3 4 5 6
2 3 (unused) 4
Figure 6.7 Sector slip processing
214
7 8
5 6 212
215 216
213 214
C141-E042-01EN