Maxtor D540X-4K - Manual (Page 62)

Basic Principles of Operation
5-14 Maxtor D540X-4K 20.4/40.0/60.0/80.0 GB AT
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The Maxtor D540X-4K drives use two techniques for replacing defective sectors -
inline replacement and offline replacement.
During manufacturing, if a sector on a cylinder is found to be defective, the address
of the sector is added to the drive's defect list. The defective sector is “skipped,” and
is replaced by the next immediate sector, which maintains a sequential ordering of
logical blocks. This inline sparing technique is employed in an attempt to eliminate
slow data transfer that would result from requiring a seek to another cylinder to access
a replacement sector.
The Maxtor D540X-4K drives are divided into 30 logical zones for purposes of defect
management. Each zone has a pool of 32 spare sectors, which are reserved for offline
replacement.
Defects that occur in the field are known as grown defects. If such a defective sector
is found in the field, the sector is reallocated to a spare sector from the nearest available
pool of spares. The defect list supports a maximum of 500 grown defects.
Sectors are considered to contain grown defects if the quadruple-burst ECC algorithm
must be applied to recover the data. If this algorithm is successful, the corrected data
is stored in the newly allocated sector. If the algorithm is not successful, a pending
defect will be added to the defect list. Any subsequent read to the original logical block
will return an error if the read is not successful. A host command to over-write the
location will result in several write/read/verifies of the suspect location. If any of these
operations fail, the new data will be written to a spare sector, and the original location
will be added to the permanent defect list. If all of the operations are successful, data
will be written to the location, and the pending defect will be removed from the list.