[linux-lvm] Restoring snapshot gone bad
zkabelac at redhat.com
Fri Sep 22 08:11:27 UTC 2017
Dne 22.9.2017 v 08:03 Mauricio Tavares napsal(a):
> I have a lv, vmzone/desktop that I use as drive for a kvm guest;
> nothing special here. I wanted to restore its snapshot so like I have
> done many times before I shut guest down and then
> lvconvert --merge vmzone/desktop_snap_20170921
> Logical volume vmzone/desktop is used by another device.
> Can't merge over open origin volume.
> Merging of snapshot vmzone/desktop_snap_20170921 will occur on next activation
> of vmzone/desktop.
> What is it really trying to tell me? How to find out which other
> device is using it?
When you want merge a snapshot - origin must be an unused volume (so not
Merging process 'copies/restores' modified blocks in your origin volume - thus
i.e. filesystem would not be able to handle 'changes' happening underneath its
So if there are not condition which let you start snapshot merge, the
operation is delayed - likely your 'next' activation of your origin volume in
which case it's pretty sure there is no user so the merge can be started
(or you can 'lvchange --refresh')
> lvdisplay tells me that
> lvdisplay /dev/vmzone/desktop
> --- Logical volume ---
> LV Path /dev/vmzone/desktop
> LV Name desktop
> VG Name vmzone
> LV UUID 3hcB1L-rIRf-PHZQ-I55F-ZXhT-SnSZ-vThO8U
> LV Write Access read/write
> LV Creation host, time duocismj01e9se, 2017-06-29 15:07:12 -0400
> LV snapshot status source of
> desktop_snap_20170921 [active]
> LV Status available
> # open 2
here you can see 'non-zero' open count
> LV Size 100.00 GiB
> Current LE 25600
> Segments 1
> Allocation inherit
> Read ahead sectors auto
> - currently set to 256
> Block device 252:6
> When I do plain old lvs (or lvs -a -o +devices), the attribute entry
> for the desktop looks like
> desktop vmzone Owi-aos--- 100.00g
> According to https://linux.die.net/man/8/lvs the "O" in Owi-aos--- means it
> is merging a snapshot. But, what is its status? Based on how long it
> has been that way, I think it is hung but I do not know what is
> causing this hangup.
Nothing is hanging - it's just postponed for next opportunity...
Progress of merging can be checked easily with command 'lvs'.
Note: while the merging is in progress - you can already use 'merged origin'
so i.e. if you merge snapshot of you 'root' volume - on reboot and next
activation you can already use 'merged' result while actually copying is
processed in the background and you can check its progress percentage.
More information about the linux-lvm