Defect Management; Automatic Defect Retirement; 3.9.10 Error Recovery Process; Hot Plug Support - Western Digital WD15NPVX Technical Reference Manual

WD Green MB500M-6Gb
determine whether a system problem is the result of a hard drive failure or other component
malfunction. Error Logging retains total error count for the life of the drive and complete records for
the last five errors.
3.9.8
Every WD drive undergoes factory-level intelligent burn in, which thoroughly tests for and maps out
defective sectors on the media before the drive leaves the manufacturing facility. Following the factory
tests, a primary defect list is created. The list contains the cylinder, head, and sector numbers for all
defects.
Defects managed at the factory are sector slipped. Grown defects that can occur in the field are mapped
out by relocation to spare sectors on the inner cylinders of the drive.
3.9.9
The automatic defect retirement feature automatically maps out defective sectors while reading or
writing. If a defective sector appears, the drive finds a spare sector.
The following item is specific to automatic defect retirement on writes (write auto-relocation):
Data is always written to disk (using automatic defect retirement if required) and no error is
reported.
The following item is specific to automatic defect retirement on reads (read auto-relocation):
When host retries are enabled, the drive will internally flag any unrecoverable errors (DAMNF or
ECC). This flagging allows subsequent write commands to this location to relocate the sector only
if the sector test fails.

3.9.10 Error Recovery Process

The drive has the following means of Error Recovery:
One-the-Fly Recovery: Using LDPC's internal recovery mechanism with Global and Local
Iteration for Error Recovery and Correction. This recovery is real time and does not require any
additional re-reads for the correction.
Simple Firmware Assist Recovery: Single variable re-reads involving off-track recoveries and synch
mark retires.
Extended Firmware Assist Recovery: This retry procedure will step through a combination of
positive/negative track offsets and VGA DAC manipulations to recover the data. In addition,
further retries will also involve Low Pass Filter (FIR) manipulations, Timing recovery, and Synch
Error Recoveries deeper into the retry process. Furthermore, in specific retry steps Hardware assist
is also involved for Extended Retry involving more modification of FIR filters & Erasure Sweep.
LDPC Erasure Sweep Correction: This step sweeps the entire data stream with a Erasure Length
and a Sliding Window, both programmable, to maximize the correction capability.
When an extended retry operation is successful, the controller continues with the command. The
controller clears any changes during the F/W Assist Recovery before commencing to the next
operation.
3.10

Hot Plug Support

SATA supports hot plugging (also known as "hot swapping"), the ability to swap out a failed hard drive
without having to power down the system or reboot. This capability contributes to both data
availability and serviceability without any associated downtime, making it a critical feature for
extending SATA into enterprise applications.
WD SATA drives support hot plugging only in systems where a SATA hard drive storage backplane is
used.
2679-771422-A00

Defect Management

Automatic Defect Retirement

RELEASED 5/2/13 (WD CONFIDENTIAL)
Product Features
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