Write Safety; Data Buffer Test; Error Recovery; Automatic Reallocation - IBM IC25N020ATDA04 - Travelstar 20 GB Hard Drive Specifications

5.4 WRITE safety

The drive ensures that the data is written into the disk media properly. The following conditions are
monitored during a write operation. When one of these conditions exceeds the criteria, the write operation
is terminated and the automatic retry sequence is invoked.
! Head off track
! External shock
! Low supply voltage
! Spindle speed out of tolerance
! Head open/short

5.5 Data buffer test

The data buffer is tested at power on reset and when a drive self-test is requested by the host. The test
consists of a write/read '00'x and 'ff'x pattern on all buffers.

5.6 Error recovery

Errors occurring on the drive are handled by the error recovery procedure.
Errors that are uncorrectable after application of the error recovery procedure are reported to the host
system as nonrecoverable errors.

5.7 Automatic reallocation

The sectors that show some errors may be reallocated automatically when specific conditions are met.
The drive does not report any auto reallocation to the host system. The conditions for auto reallocation are
described below.

5.7.1 Nonrecovered write errors

When a write operation cannot be completed after the Error Recovery Procedure (ERP) is fully carried out,
the sector or sectors are reallocated to the spare location. An error is reported to the host system only
when the write cache is disabled and the auto reallocation has failed.

5.7.2 Nonrecoverable read error

When a read operation fails after the ERP is fully carried out, a hard error is reported to the host system.
This location is registered internally as a candidate for the reallocation. When a registered location is
specified as a target of a write operation, a sequence of media verification is performed automatically.
When the result of this verification meets the required criteria, this sector is reallocated.

5.7.3 Recovered read errors

When a read operation for a sector fails and is recovered at the specific ERP step, the sector is reallo-
cated automatically. A media verification sequence may be run prior to the reallocation according to the
predefined conditions.
Travelstar 48GH, 30GN & 15GN hard disk drive specifications
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