IBM DBCA-204860 Hard Drive Specifications - Page 95
Reassign Function
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10.11 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. The assured number of the spare sectors is a minimum of 3795 sectors. 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 disabled automatically. The spare sectors for reassignment are located at reserved area. As a result of reassignment, the physical location of logically sequenced sectors will be dispersed. 10.11.1 Auto Reassign Function The sectors that show some errors may be reallocated automatically when specific conditions are met. The spare sectors for reallocation are located at reserved area. The conditions for auto-reallocation are described below. When a device shipped from IBM, a minimum of 791 usable spare sectors are available. Non recovered write errors When a write operation can not 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 fails. If the number of available spare sectors reaches 16 sectors, the write cache function will be disabled automatically. If the command is without retry and the write cache function is disabled, the auto reassign function is not invoked. Non recovered read errors When a read operation fails after defined E R P is fully carried out, a hard error is reported to the host system. This location is registerred internally as a candidate for the reallocation. When a registerred 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 criteria, this sector is reallocated. Recovered read errors When a read operation for a sector failed once then recovered at the specific E R P step, this sector of data is reallocated automatically. A media verification sequence may be run prior to the relocation according to the pre-defined conditions. General Operation Descriptions 87