RE: RAID 5 or RAID 6: Which should you select?
You lightly touched on one major aspect of today's drives and inherent problems within: error correction on perfectly good drives.
Simply put, there's a massive amount of overhead on today's drives given the manufacturer's acceptable hardware tolerance for error correction. Read your drive specs, I think you'll be surprised.
The rule of thumb is the larger drive space you have, the larger allotted error correction time; which = cpu peformance overhead.
Life's great when we can store the equivalent of the Library of Congress on a few arrays. Nonetheless, one cannot simply ignore the data errors that exist on perfectly functioning drives. IT folks that don't factor in the leakage of errors are doomed to long hours of chasing the blame game from the upper echelon screaming "I thought this system was going to be reliable!!!"
Well Sir, it is, sort of.
Factor in aging drive spindle noise, worn internal mechanical components of the drive- and you have all the makings of a king size headache.
The bottom line is this: in any disk array, there are trade-offs in performance, integrity, and finally, cost.
Therefore, the reality of which array and which architecture to select must come down to two things: first, data integrity. Just how good is it? Secondly, cost. You can't ignore the CFO and their insistence to remain within a sane budget.
Anything less than that and you will fall into that age old trap of 'head in sand' viewpoint, and it WILL come back to bite you.
