On Tue, 25 Jun 2013, Frank Leonhardt wrote:
Couldn't agree more! In fact the whole disk mirroring thing still
confuses me, as there are too many options and no guide for choosing
between them. As far as I understand it, gmirror is the way to go in
most cases because you end up with two identical drives, either of
which can be salvaged from the wreckage after a crash, stuck in to
another PC and booted. ZFS is the solution if you want to spread lots
of data across lots of drives.
ZFS can do mirrors, too, and almost everything else. Its weakness now
is that it is relatively memory hungry. So I would advise this:
gmirror(8) for data safety on machines with relatively limited memory.
graid(8) for software BIOS RAID.
ZFS for mirrors or more typical RAID arrays on machines with 4G of
memory or more.
Actually, in practical terms, I don't see why ZFS is better than pairs
(or threes) of gmirrored drives mounted on to one file system in the
traditional way. Perhaps I just don't get it, or perhaps I'm just too
traditional to give up on the idea that it's good to know which drive
a particular file is on.
It's RAID, so you get more space than mirrors, and possibly better
performance for some things. ZFS RAID-Z1 (and -Z2, -Z3) have a lower
vacuum coefficient than RAID-5. There are lots of nifty features, like
being able to add storage without reformatting.
There are other options, but I suspect the three above cover most of the
needs and are what we should be suggesting to new users in the Handbook.
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