Richard Elling - PAE wrote:
Incidentally, since ZFS schedules the resync iops itself, then it can
really move along on a mostly idle system. You should be able to resync
at near the media speed for an idle system. By contrast, a hardware
RAID array has no knowledge of the context of the data or the I/O
scheduling,
so they will perform resyncs using a throttle. Not only do they end up
resyncing unused space, but they also take a long time (4-18 GBytes/hr
for
some arrays) and thus expose you to a higher probability of second disk
failure.
Just as an other data point: It is true that the array doesn't know the
context of the data or the i/o scheduling but some arrays do watch the
incoming data rate and throttle accordingly. (T3 used to for example.)
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