Reassign Function; Auto Reassign Function - Hitachi 7K400 - Deskstar Hard Drive Specifications

10.12 Reassign function

The Reassign function is used with read commands and write commands. The sectors of data for reassignment are
prepared as the spare data sector.
This reassignment information is registered internally and the information is available right after completing the
Reassign function. Also the information is used on the next power on reset or hard reset.
If the number of the spare sector reaches 0 sector, the Reassign function will be automatically disabled.
The spare sectors for reassignment are located at regular intervals from Cylinder 0. As a result of reassignment the
physical location of logically sequenced sectors will be dispersed.

10.12.1 Auto Reassign function

The sectors which show some errors may be reallocated automatically when specific conditions are met. The spare
tracks for reallocation are located at regular intervals from Cylinder 0. The conditions for auto- reallocation are
described below.
Nonrecovered write errors
• When a write operation cannot be completed after the Error Recovery Procedure (ERP) is fully carried
out, the sector(s) 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. If the Write Cache function is
ENABLED when the number of available spare sectors reaches 0 sector, both Auto Reassign function
and Write Cache function are automatically disabled.
Nonrecovered read errors
• When a read operation has failed after defined ERP is fully carried out, a hard error is reported to the
host system. This location is registered internally as a candidate for reallocation. When a registered
location is specified as a target of a write operation, a sequence of media verification is performed auto-
matically. When the result of this verification meets the criteria, this sector is reallocated.
Recovered read errors
• When a read operation for a sector has failed once and then has recovered at the specific ERP step, this
sector of data is automatically reallocated. A media verification sequence may be run prior to the reallo-
cation according to the predefined conditions.
Deskstar 7K400 Hard Disk Drive Specification
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