Hiya,
I hope you could help me on this:
in short:
is it possible to create a snapshot LV of an original LV
but in a different volume group?
or alternatively, what's the best way to bring up a LV in a VG
that is missing a PV (as in a disk crash) if that LV has all its
extents on still sane PVs?
in long:
basically, this is what I would like to do:
I have two disks, not as much as I would like, and I want:
- to have 100GB of data mirrored (using Linux software raid
(mdadm)) on 2 disks so that it survives disk crashs
- to make a number of frequent snapshots of that data to
be able to restore things in case of human errors.
- (and I also want to have some "striped" storage space for
worthless data).
BUT, I don't want to have the snapshot volumes mirrored.
My initial idea was to have 2 volume groups: a "safe" one with
only one /dev/md0 PV and an "unsafe" one with the striped LVs
and the snapshots.
However I couldn't find how to create snapshots of the LVs in
"safe" into the "unsafe" VG. It seems to me that it should be
possible, shouldn't it?
Anyway, then I merged the two "safe" and "unsafe" VGs into one
"vol" VG. Now I can make snapshots of the LV physically located
on /dev/md0 into the "unsafe" area.
But if one of the disks fails, /dev/md0 will still be available
but the "vol" VG won't be able to come up because of the other
missing PVs.
If such a thing happen, I can happily live with the missing
snapshots and "unsafe" storage for a while until I buy a
replacement HD, but how should I do about making sure that the
/dev/md0 filesystem is still available in the mean time?
Or is there a more straightforward way to achieve this that I
haven't thought of?
TIA,
Stephane
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