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FUJITSU MPG3XXXAH-E User Manual

Page 189

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C141-E116-01EN

6 - 12

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Alternate cylinder assignment

A defective sector is assigned to the spare sector in the alternate cylinder.

This processing is performed when a physical track contains three or more defective sectors, and
when the automatic alternate processing is performed.

Figure 6.8 shows an example where (physical) sector 5 is detective on head 0 in cylinder 0.

5

7

6

4

3

1

736

735

2

Index

Cylinder 0

Head 0

Head 0

Already

assigned

Defective

sector

4 alternate cylinders are provided for each head in zone 13 (inner side).

When an access request to sector 5 is specified, the device accesses the alternated sector in the
alternate cylinder instead of sector 5. When an access request to sectors next to sector 5 is
specified, the device seeks to cylinder 0, head 0, and continues the processing.

Defective sector is assigned to unassigned sector.

(unused)

Sector (logical)

Sector (physical)

Alternate
cylinder

2

1

4

3

6

7

736

735

Figure 6.8

Alternate cylinder assignment

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Automatic alternate assignment

The device performs the automatic assignment at following case.

1) 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.

2) When a write error occurs and the error does not recovered.

1 alternate cylinder is provided in outer side.