> an array of 30 drives in a RaidZ2 configuration with two hot spares
> I don't want to mirror 15 drives to 15 drives
ok, so space over speed... and are willing to toss somewhere between 4
and 15 drives for protection.
raidz splits the (up to 128k) write/read recordsize into each element of
the raidz set.. (ie: all drives must be touched and all must finish
before the block request is complete) so with a 9 disk raid1z set that's
(8 data + 1 parity (8+1)) or 16k per disk for a full 128k write. or for
a smaller 4k block, that a single 512b sector per disk. on a 26+2 raid2z
set that 4k block would still use 8 disks, with the other 18 disks
unneeded but allocated.
so perhaps three sets of 8+2 would let three blocks be read/written to
at once with a total of 6 disks for protection.
but for twice the speed, six sets of 4+1 would be the same size, (same
number of disks for protection) but isn't quite as safe for its 2x speed.
Rob
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