zfs on gmirror slice

Mark Stapper stark at mapper.nl
Wed Sep 2 08:49:29 UTC 2009

Thomas Backman wrote:
> On Sep 2, 2009, at 10:27 AM, Mark Stapper wrote:
> Nothing a LiveCD or something to that regard can't handle. Obviously
> this doesn't work for everyone, but it should for many.
Actually it won't because updating zfs comes with updating your world.
After updating you world, you will be running a newer ZFS version then
the one that come with the RELEASE install, hence the need to update
your zfs filesystems. Incidentally, the livefs CD contains the "old" zfs
version. You see where I'm going?

You could, of course, copy the base system to a USB drive, boot from it,
and so sidestep the whole "can't unmount root" problem, but it's hard to
insert a USB device over ssh... ... ...
>> self-healing sounds very nice, but with mirrorring you have data on two
>> discs, so in that case there no "healing" involved, it's just
>> checksumming and reading the non-corrupted copy.
>> From the gmirror manpage: "All operations like failure detection, stale
>> component detection, rebuild of stale components, etc. are also done
>> automatically."
>> This would indicate the same functionality, with a much less fancy name.
>> However, i have not tested it the way they demonstrate zfs's
>> "self-healing" property.
>> I might, if I get the time to run it in a virtual machine one of these
>> days..
> If ZFS finds a corrupted copy and a non-corrupted one in a mirrored
> ZFS pool, it will repair the damage so that both copies are valid, so
> yes, self-healing will indeed occur. :)
I'm feeling Shakespearean again... My point was that I find
"self-healing" too magic sounding. While indeed it means:"Automatic data
error detection and rebuilding" or something along those lines. We don't
call the automatic remapping of bad sectors in HDD's "self-healing" do we?
Alas, I must admit that on file-system level, some "healing" does take

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