On Tue, 8 Nov 2011, Jim Klimov wrote:

Second question regards single-HDD reliability: I can
do ZFS mirroring over two partitions/slices, or I can
configure "copies=2" for the datasets. Either way I
think I can get protection from bad blocks of whatever
nature, as long as the spindle spins. Can these two
methods be considered equivalent, or is one preferred
(and for what reason)?

Using two partitions on the same disk seems to give you most of the headaches associated with more disks without much of the benefit. If there is any minor issue, you will see zfs resilvering partitions and resilvering will be slow due to the drive heads flailing back and forth between partitions. There is also the issue that the block allocation is not likely to be very efficient in terms of head movement if two partitions are used.

Bob Friesenhahn
bfrie...@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/
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