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 in case that a physical track contains one or two defective sectors (2 sectors/track)
2)Spare cylinder for track slip:
used for alternative assignment for the third and subsequent defective sectors in case that a physical track contains three or more defective sectors, and also used by automatic alternative assignment (78 cylinders/drive).
3)Spare cylinder for alternative assignment:
used for automatic alternative assignment (1 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.
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1 | 2 | 3 | 4 | 5 |
| 6 | 7 | 8 |
| 29841 |
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| 29942 |
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| 300243 |
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Cylinder 0 |
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| Defective |
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| SP |
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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 | 240 |
| 241 |
| 242 |
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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 |
