[linux-lvm] exposing snapshot block device
Tomas Dalebjörk
tomas.dalebjork at gmail.com
Mon Sep 7 17:37:41 UTC 2020
thanks
ok
vgsplit/merge instead
and after that lvconvert-s
yes, I am aware of the issues with corruption
but if the cow device has all data, than no corruption will happen, right?
if COW has a copy of all blocks
than a lvconvert —merge, or mount of the snapshot volume will be without issues
right?
regards Tomas
Sent from my iPhone
> On 7 Sep 2020, at 18:42, Zdenek Kabelac <zkabelac at redhat.com> wrote:
>
> Dne 07. 09. 20 v 18:34 Tomas Dalebjörk napsal(a):
>> thanks for feedback
>> so if I understand this correctly
>> # fallocate -l 100M /tmp/pv1
>> # fallocate -l 100M /tmp/pv2
>> # fallocate -l 100M /tmp/pv3
>> # losetup —find —show /tmp/pv1
>> # losetup —find —show /tmp/pv2
>> # losetup —find —show /tmp/pv3
>> # vgcreate vg0 /dev/loop0
>> # lvcreate -n lv0 -l 1 vg0
>> # vgextend vg0 /dev/loop1
>> # lvcreate -s -l 1 -n lvsnap /dev/loop1
>> # vgchange -a n vg0
>> # lvconvert —splitsnapshot vg0/lvsnap
>> # vgreduce vg0 /dev/loop1
>
>
> Hi
>
> Here you would need to use 'vgsplit' rather - otherwise you
> loose the mapping for whatever was living on /dev/loop1
>
>> # vgcreate vg1 /dev/loop2
>> # lvcreate -n lv0 -l 1 vg1
>> # vgextend vg1 /dev/loop1
>
> And 'vgmerge'
>
>
>> # lvconvert -s vg1/lvsnap vg1/lv0
>> not sure if the steps are correct?
>
>
> I hope you realize the content of vg1/lv0 must be exactly same
> as vg0/lv0.
>
> As snapshot COW volume contains only 'diff chunks' - so if you
> would attach snapshot to 'different' lv - you would get only mess.
>
>
> Zdenek
>
More information about the linux-lvm
mailing list