Re: Anybody using RAID 6+2? ... Is BAARF still Valid ?

hmmm, well normally  RAID n+m  means

apply raid n THEN apply RAID m. so 6+2 would mean build RAID6 sets and then
RAID them using RAID2.

Unfortunately this makes no sense whatsoever for a RAID system since it
would mean

1. Build RAID stripes with redundant parity blocks - RAID6.
2. Stripe 39 (or perhaps 79 if its a 64 bit system) of these sets at the bit
level with error correction (using something I don't understand called a
hamming code).

So I'm guessing the +2 means either something the disk vendor made up
or redundant
parity - which is implied by RAID6 anyway.

As for whether BAARF applies to SAN storage then my take is that it does,
with the rather important caveat that it only matters if the storage
subsystem is, or is likely to become, the primary bottleneck on the system.
Or to put it another way for many systems the efficiency of your disk
subsystem is the least of your worries.

I ought to acknowledge
http://en.wikipedia.org/wiki/Redundant_array_of_independent_disks for some
of this post - and for the BAARF folks to add to if they so desire - any
errors are of course my fault and not the wiki's




--
Niall Litchfield
Oracle DBA
http://www.orawin.info

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