Javier Guerra schrieb:
On Wed, Feb 25, 2009 at 8:20 AM, Tomasz Chmielewski <mangoo@xxxxxxxx> wrote:
Is it possible to make snapshots when using raw devices (i.e. disk,
partition, LVM volume) as guest's disk image?
According to documentation[1] (and some tests I made) it is only possible
with qcow2 images. Which makes it very inflexible:
- one is forced to use a potentially slower file access
- one can't use the benefits of i.e. iSCSI disk access, SAN etc.
what about using 'good' block devices, and add one small, mostly empty
qcow2? could it be used to store the snapshot for all? of course it
would degrade performance while it's active, but should revert after
'commiting' it to the 'real' block device(s)
It doesn't work for me - I get:
qm> savevm 1
Error while creating snapshot on 'virtio0'
Where "virtio0" is my "real" block device. I guess it still wants to
write a snapshot there, as outlined in the documentation:
"The VM state info is stored in the first qcow2 non removable and
writable block device. The disk image snapshots are stored in every
disk image."
Or, am I making a mistake here?
Besides:
- guest will see this second device - not needed
- still, we save the state of disks, but we don't need it for tasks like
"pausing guest, upgrading kernel on host, rebooting host, resuming guest"
--
Tomasz Chmielewski
http://wpkg.org
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