From: "Rich Gauszka" 

http://www-5.ibm.com/storage/europe/pdfs/raid_methods_nas.pdf

RAID 5E (Enhanced) puts hot spares to work to improve reliability and
performance. A hot spare is normally inactive during array operation and is
not used until a drive fails. By utilizing unallocated space on the drives
in the array, a "virtual" hot spare is created. By putting the
hot spare to work, performance improves because more "heads" are
writing the data. In the event of a drive failure, the RAID controller will
start rearranging the data from the failed disk into the spare space on the
other drives in the array. Thus, with RAID 5E, you receive the advantages
of RAID 5, but with additional performance provided by putting the hot
spare to work

"Geo."  wrote in message news:40550031{at}w3.nls.net...
> Why is distributed hot spare an advantage? Seems to me a hot spare where
the
> disk spins down when not in use is more likely to not put the wear on the
> spare drive that a distributed hot spare would, no? (am I missing
something
> about this, I've never looked into it before)
>
> Geo.
>
> "Rich Gauszka"  wrote in message
> news:40548599$1{at}w3.nls.net...
> > RAID 5E uses a distributed hot spare disk, so it works with a minimum of
> > four disks. Protection: very good. Capacity: N-2. Where N is the number
of
> > disks, the capacity is N-2 (one for parity and one for spare).
> >
> > http://www.mckinnonsc.vic.edu.au/la/it/ipmnotes/security/raid.htm
>
>
>

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