On Mon, Mar 13, 2000 at 08:40:57AM -0500, Chris Mauritz wrote:
> I'm going to start using them for applications where the data is expendible
> (mp3 jukebox comes to mind) where I just want a cheap RAID 0 array to hold a
> big chunk of bits. Another good application might be large web farms where
> the data on any one web server can go poof without any problems and you can
> then stripe a pair of inexpensive IDE disks for better throughput on a
> budget. When you're talking 10's or 100's of servers, the savings adds up.
> With 40gig ATA66 drives going for under $300 these days (and 10gigs in the
> $100 range), it seems like a no brainer in that kind of situation. I'd
> never use it on a busy database box, but the economics are quite compelling
> in certain situations.
You're only referring to the RAID 0 option you have with these devices.
What about RAID 1 and 10? I think particularly the latter is a good
option for low-end low-cost servers that still require some redundancy.
If you have a RAID 10 array comprised of 4 disks (i.e. a mirrored
striped pair), the likelihood of losing the entire array (i.e. either
one from each mirrored pair, or both from either plus one from the
other, or all 4 failing simultaneously) - if my probability theory is
not entirely rusty - is (2n+1)squared divided by n to the power of 4 if
the probability of losing a single disk is the inverse of n (how do you
write this stuff properly using just ascii?) which approaches the
inverse of n squared if n is large enough; which means that since n is
pretty big (the probability of one of today's IDE drivers failing is
pretty low), RAID 10 is not significantly worse than RAID 1 in terms of
inherent redundancy, whilst being significantly faster.
- Frank
--
frank joerdens
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