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Re: Dealing with domUs state

On 04/11/10 15:26, Joel Carnat wrote:

I am running NetBSD 5.0_STABLE/amd64 with xenkernel33-3.3.1nb1.
I have a Windows domU that I'd like to backup from times to times.
In software like VMware or VirtualBox, there is a feature called
"snapshots" which enables to save a full state (memory, disk...) of a
VM. This is a really convinient way to test patches or software.

The only method I found on nbsd/xen was to shutdown the domU, copy the
disk image file and start the domU. When I want to go back to a previous
state, I stop the domU, replace the disk image and start the domU.

Basically, snapshotting follows these criterias:
1 -bring/wait for the system to be in a coherent state
2 - save the state
3 - restore it

YMMV, I have not tested it with a HVM domU; snapshoting is a special case of save/restore cycle, in a rapid succession:
- xm save HVM domU
- snapshot the disk image (either through dd, lvm, or qcow - it all depends on the kind of block image you chose for your HVM domU)
- xm restore HVM domU

Is there some "better" way to deal with domU snapshots ?
Especially ways that would enable to have to domU stil running when
backuping and/or restoring ?


PS: the domU is hosted on a local FFSv2 partition, with "log" enabled.

For HVM, see above; for PV guests, my branch (jym-xensuspend) contains the necessary stuff (steps would be exactly the same though: save/snapshot hd/restore), but it needs more testing before I merge it.

Jean-Yves Migeon

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