[Beowulf] RE: Storage - the end of RAID?
Lux, Jim (337C)
james.p.lux at jpl.nasa.gov
Fri Oct 29 11:06:03 PDT 2010
> -----Original Message-----
> From: beowulf-bounces at beowulf.org [mailto:beowulf-bounces at beowulf.org] On Behalf Of Hearns, John
> Sent: Friday, October 29, 2010 9:43 AM
> To: beowulf at beowulf.org
> Subject: [Beowulf] Storage - the end of RAID?
> Quite a perceptive article on ZDnet
> Class, discuss.
Yes, indeed, his comments makes sense..
After all, the acronym was "Redundant Arrays of Inexpensive Disks"
Granted, these implementations had useful side effects (e.g. improving read speed by sharing)
The real question is whether drive reliability has improved commensurate with the drive capacity (that is, is the failure rate per drive basically constant, as opposed to the "bit error rate")
RAID was designed to solve the "failed drive" problem, more than the "bad bit" problem. And to do it using a less than "rate 1/2" code.. that is, rather than store 2 copies of your data, you could store, essentially, 11/8ths copies of your data (using a Hamming code to generate 3 syndrome bits for each 8 data bits for instance), thereby saving money.
However, if drives get cheap, then using 2 copies (or 3) isn't a big deal.
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