Not that I'm encouraging anyone to use RAID -- I think it is an
obsolete technology -- but if you insist, you should know this...
Detailed info from Western Digital on the difference between their
consumer/desktop hard drives and enterprise drives commonly used in
RAID applications...
Question: What is the difference between Desktop edition and RAID
(Enterprise) edition hard drives?
Answer: Western Digital manufactures desktop edition hard drives and
RAID Edition hard drives. Each type of hard drive is designed to work
specifically in either a desktop computer environment or a demanding
enterprise environment.
If you install and use a desktop edition hard drive connected to a
RAID controller, the drive may not work correctly unless jointly
qualified by an enterprise OEM. This is caused by the normal error
recovery procedure that a desktop edition hard drive uses.
When an error is found on a desktop edition hard drive, the drive will
enter into a deep recovery cycle to attempt to repair the error,
recover the data from the problematic area, and then reallocate a
dedicated area to replace the problematic area. This process can take
up to 2 minutes depending on the severity of the issue. Most RAID
controllers allow a very short amount of time for a hard drive to
recover from an error. If a hard drive takes too long to complete this
process, the drive will be dropped from the RAID array. Most RAID
controllers allow from 7 to 15 seconds for error recovery before
dropping a hard drive from an array. Western Digital does not
recommend installing desktop edition hard drives in an enterprise
environment (on a RAID controller).
Western Digital RAID edition hard drives have a feature called TLER
(Time Limited Error Recovery) which stops the hard drive from entering
into a deep recovery cycle. The hard drive will only spend 7 seconds
to attempt to recover. This means that the hard drive will not be
dropped from a RAID array. Though TLER is designed for RAID
environments, it is fully compatible and will not be detrimental when
used in non-RAID environments.
http://www.macintouch.com/readerreports/harddrives/index.html#d19nov2009
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