6.4.1Spare area
Following two types of spare area are provided in the user space.
1)Spare sector for sector slip:
used for alternating defective sectors at formatting in shipment (255 sectors/60 cylinder)
2)Spare cylinder for alternative assignment:
used by automatic alternative assignment. (4 cylinder/drive)
6.4.2Alternating 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.
Index |
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| Sector (physical) |
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1 | 2 | 3 | 4 | 5 |
| 6 | 7 | 8 |
| 298622 |
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| 623299 |
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| 300624 |
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Cylinder 0 |
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| Defective |
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Head 0 |
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| sector |
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1 | 2 | 3 | 4 |
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| 5 | 6 | 7 | 621 |
| 622 |
| 623 |
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| Sector (logical) | unused |
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If an access request to sector 5 is specified, the device accesses physical sector 6 instead of sector 5.
Figure 6.7 Sector slip processing
| 6 - 11 |
