Re: RAID stripe size (was: 5.1 RAID5 write performance)

[der Mouse <mouse%Rodents-Montreal.ORG@localhost>]

> So, what's the advantage of a larger sectPerSU?

Larger is not necessarily better.  Larger than the typical write size
(which is usually the filesystem block or frag size) is actually a
*dis*advantage, because it means that common writes force RMW cycles.

Much smaller than the typical access size is a different disadvantage.
In particular, accesses larger than sectPerSU force additional drives
to pay seek, rotational latency, and contention penalties.  (This
applies to both read and write, though in slightly different ways.)

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