Seagate Elite 47 ST446452W, Руководство по эксплуатации продукта

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Elite 47 Product Manual, Rev. A 29
7.0 Defect and error management
The drive, as delivered, complies with this product manual. The read error rate and specified storage capacities
are not dependent on using defect management routines by the host (initiator).
Defect and error management in the SCSI system involves the drive internal defect/error management and
SCSI systems error considerations (errors in communications between initiator and the drive).
7.1 Drive internal defects and errors
During the initial drive format operation at the factory, media defects are identified, tagged as being unusable,
and their locations recorded on the drive primary defects list (referred to as the “P” list and also as the EFT
defect list). At factory format time, these known defects are also reallocated, that is, reassigned to a new place
on the medium and the location listed in the defects reallocation table. The “P” list is not altered after factory
formatting. Locations of defects found and reallocated during error recovery procedures after drive shipment
are listed in the “G” list (defects growth list). The “P” and “G” lists may be referenced by the initiator using the
Read Defect Data command (see Section 5.2.1.2 in the
SCSI Interface Product Manual, part number
77738479).
7.2 Drive error recovery procedures
Whenever an error occurs during drive operation, the drive, if programmed to do so, performs error recovery
procedures to attempt to recover the data. The error recovery procedures used depend on the options previ-
ously set up in the error recovery parameters mode page. Error recovery and defect management may involve
the use of several SCSI commands, the details of which are described in the
SCSI Interface Product Manual.
The drive implements selectable error recovery time limits such as are required in video applications. For addi-
tional information on this, refer to Table 5.2.1-22 in the
SCSI Interface Product Manual
which describes the
Mode Select/Mode Sense Error Recovery parameters.
The error recovery scheme supported by the drive provides a means to control the total error recovery time for
the entire command in addition to controlling the recovery level for a single LBA. The total amount of time spent
in error recovery for a command can be limited via the Recovery Time Limit bytes in the Error Recovery Mode
Page. The total amount of time spent in error recovery for a single LBA can be limited via the Read Retry Count
or Write Retry Count bytes in the Error Recovery Mode Page.
The drive firmware error recovery algorithms consist of 16 levels for read recoveries and 12 levels for writes.
Each level may consist of multiple steps, where a step is defined as a recovery function involving a single re-
read or re-write attempt. The maximum level used by the drive in LBA recovery is determined by the Read and
Write Retry Counts.
Table 3 equates the Read and Write Retry Count with the maximum possible recovery time for read and write
recovery of individual LBAs. The times given do not include time taken to perform reallocations, if reallocations
are performed. The ARRE bit enables/disables reallocations, but if the RC bit is one, it takes precedence over
ARRE to disable auto reallocation. When the drive has read all of the called for data, it does not go back and
reallocate any sectors of erroneous data that were not reallocated because the RC bit was one. The drive does
not report an unrecovered error when RC is one.