On 09/08/2010 05:49 PM, Von Fugal wrote:
So I don't know where to start looking for the answer to this, maybe I'm
thinking about it all wrong. I've googled LVM copy, pvmove etc. to no
avail.
What I want to do is add a new disk to a vg and retire an old disk. I've
been burned before badly though with just using pvmove, where minutes
after the move is completed the 'new' (not really so new) drive goes bad
and the old drive is already 'gone' from the lv. This is not really so
out there what with the extensive IO done on the 'new' drive. If it was
at all thinking of going bad... it probably will. What I would like to
do is copy the contents of the old pv to the new pv, but while still
persisting the data in a sort of mirror on the old pv for a time. When
things check out, then I want to just vgreduce oldpv and be done with
it. I realize I could use lvconvert to turn the concerned lv into a
mirrored lv, but when it comes time to remove the old pv, it becomes
very klunky to remove the target pv from the mirror, keeping the new
one, specifying devices ad nauseum. As well, it makes things even more
klunky if you have more than one lv on the old pv you're trying to get
rid of 'safely'. It seems like this would be something that lvm could
handle exceptionally, but I'm at a loss. Any suggestions?
Von Fugal
I haven't done a pvmove on commodity hardware, but the last time I did a
pvmove, the vg got confused about where the extents were and stopped
somewhere in the middle. As the extents are all still there on the
original disk, I did an lvmcfgrestore to the previous config (lvm2 keeps
a few config backups around just in case), ran an xfscheck, and
restarted the pvmove. Worked great.
To put it in perspective, I only had 2 or 3 of these mid-move failures.
I was moving around 50 or 60 physical volumes at the time.
It sticks in my mind that there was an option for pvmove to mirror the
entire pv before removing the old drives extent maps, but I might be
thinking about mirroring on lvm releases with a less reliable pvmove. I
read somewhere about one person's pvmove nightmares, after which they
would only mirror the PVs instead of pvmoving things around. I've not
had that problem. I do have backups of my (rather large) volumes, so
venturing in the the land of lvmcfgrestore was much more relaxing (and
successful).
Where the pvmoves are highly sequential, I wouldn't expect the drive to
fail from excessive head thrashing. Maybe run badblocks on the (empty)
drive before a pvmove?
Grazie,
;-Daniel Fussell
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