On 08/20/2013 05:43 PM, Andrey Korolyov wrote:
On Tue, Aug 20, 2013 at 7:36 PM, Wido den Hollander <wido@xxxxxxxx> wrote:
Hi,
The current [0] libvirt storage pool code simply calls "rbd_remove" without
anything else.
As far as I know rbd_remove will fail if the image still has snapshots, you
have to remove those snapshots first before you can remove the image.
The problem is that libvirt's storage pools do not support listing
snapshots, so we can't integrate that.
Libvirt however has a flag you can pass down to tell you want the device to
be zeroed.
The normal procedure is that the device is filled with zeros before actually
removing it.
I was thinking about "abusing" this flag to use it as a snap purge for RBD.
So a regular volume removal will call only rbd_remove, but when the flag
VIR_STORAGE_VOL_DELETE_ZEROED is passed it will purge all snapshots prior to
calling rbd_remove.
Another way would be to always purge snapshots, but I'm afraid that could
make somebody very unhappy at some point.
Currently "virsh" doesn't support flags, but that could be fixed in a
different patch.
Does my idea sound sane?
[0]:
http://libvirt.org/git/?p=libvirt.git;a=blob;f=src/storage/storage_backend_rbd.c;h=e3340f63f412c22d025f615beb7cfed25f00107b;hb=master#l407
--
Wido den Hollander
42on B.V.
Hi Wido,
You had mentioned not so long ago the same idea as I had about a year
and half ago about placing memory dumps along with the regular
snapshot in Ceph using libvirt mechanisms. That sounds pretty nice
since we`ll have something other than qcow2 with same snapshot
functionality but your current proposal does not extend to this.
Correct, since this is about the storage pool support, that is something
completely different.
Placing custom side hook seems much more expandable than putting snap
purge into specific flag.
My proposal is a bit selfish, since I'm running into this with
CloudStack. CloudStack now has a work-around for RBD since images could
still have snapshots where other storage types are handled by libvirt.
I want to have it all handled by libvirt.
Wido
Phone: +31 (0)20 700 9902
Skype: contact42on
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--
Wido den Hollander
42on B.V.
Phone: +31 (0)20 700 9902
Skype: contact42on
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