[dm-devel] Lvm snapshot for a vm disk doubt

[Gianluca Cecchi]

Hello,
I'm in this situation and would like to be certain before doing bad things...
Thanks in advance for your help

rh el 6.1 host and a vm with one disk that is LVM based (actually it
should apply with recent upstream kernel and lvm too)

- shutdown guest
- lock exclusively the lv (because it is actually a cluster of two rh el 6.1)
on one node:
# lvchange -an /dev/VG_VIRT01/zensrv_002
on the other one:
# lvchange -aey /dev/VG_VIRT01/zensrv_002

- create snapshot
# lvcreate --size 5G --snapshot --name zensrv_002_snap /dev/VG_VIRT01/zensrv_002
 Logical volume "zensrv_002_snap" created

- power on vm going ahead doing some intrusive tests
Note that I maintained the original LV as the disk for the VM

- At the end of my work the situation I have changed about 1.7Gb of my
original disk:
# lvs /dev/VG_VIRT01/zensrv_002*
 LV              VG        Attr   LSize  Origin     Snap%  Move Log
Copy%  Convert
 zensrv_002      VG_VIRT01 owi-ao 10.00g
 zensrv_002_snap VG_VIRT01 swi-a-  5.00g zensrv_002  34.77

- Now I'm confident with the changes..
Is it ok to simply remove the snapshot?

- What if I'm not confident with the changes and would like to revert
to the original state ?
Will it do the command
lvconvert --merge /dev/VG_VIRT01/zensrv_002_snap

Or did I make it totally wrong and had to work with the snapshot and
not with the original LV????
Keep on reading docs, both rhel and general but I'm sort of confused....
Probably someone on this list already went through this way...

And could I have been working with both the LVs at the sane time (for
example creating a new vm base on the snapshot lv) and what would be
the possibile scenarios in that case?

Gianluca