Western Digital WDE2170 - Manual (Page 33)

WD Enterprise WDE2170/WDE4360 Advanced Product Features
4079-001045 Rev. B RELEASED 04-08-97 25
3.17. Error Recovery Operations
Error recovery options are set using MODE SELECT Page 1 (Read/Write Error
Recovery Page) and the Write Recovery Threshold and Read Recovery Threshold fields
in MODE SELECT Page 0 (WD Vendor Unique Page).
The drive employs a variety of recovery actions based on the type of error that occurs.
Separate recovery actions are defined for read errors, write errors, servo errors, and
drive fault errors. For a given error type, several different recovery actions may be used.
For example, read error recovery may use retries, servo track offsets, channel parameter
modification, and software ECC in an attempt to recover the error. Error information is
available to the host via the REQUEST SENSE command based on the settings in
MODE SELECT Pages 0 and 1.
The drive uses a 3-way interleaved Reed-Solomon ECC operating on 8 bit (1 byte)
symbols. On-the-fly ECC is capable of correcting single burst errors up to 1 byte per
interleave (24 bits total) with no performance degradation. On-the-fly correction is done
in hardware and cannot be disabled. The drive firmware also implements a software
ECC, which is capable of correcting single or double burst errors up to 2 bytes per
interleave.
Refer to the Western Digital SCSI Implementation Guide (document number 4096-
001116) for more information.
3.18. Self-Monitoring, Analysis, and Reporting Technology
(S.M.A.R.T.)
Self-Monitoring, Analysis and Reporting Technology (S.M.A.R.T.) is a hard drive
firmware technology that performs drive failure prediction by monitoring selected
parameters during normal drive operations. The intent of this technology is to minimize
unscheduled system downtime caused by predictable drive failures. By monitoring
selected parameters, the S.M.A.R.T. firmware can predict some drive failures before
they actually occur, allowing the user to schedule drive replacement and minimize
system interruptions.
Refer to the Western Digital SCSI Implementation Guide (document number 4096-
001116) for more information.