On Thu, Sep 9, 2010 at 7:08 PM, Anthony Liguori <anth...@codemonkey.ws> wrote: > On 09/09/2010 08:43 PM, disheng...@gmail.com wrote: >> >> From: edison<edi...@cloud.com> >> >> Add a new option when "savevm": savevm -n snapshotName, which only takes >> snapshot on disk, but doesn't save vm state(memory,cpu,devices...). >> Saving vm state on QCOW2 disk will take a long time, per my test, it will >> take 1~2 minutes to "savevm" on VM with 1G memory. Even worse, the VM is >> wholely stopped at that time, makes "savevm" not that useful. >> All we know the side effect of it:) but does it make sense to give user >> the choice? >> > > I think it would be better to explore ways to make savevm live. A round > about option would be to combine a disk-only snapshot with a live migration > to disk and somehow allow qcow2 to refer to an external memory snapshot. >
My point is we still need an interface to take online snapshot for disk-only(flush pending I/O, take QCOW2 snapshot, no savevm, no live migration), which is the fastest , lowest down time and easy to manage. Look like VMware supports such kind of operation: take a snapshot without saving memory(http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1015180). Of cause, it's better to cooperate with pv driver, or tools inside guest, which can hold I/O, flush disk cache, etc. If without such co-operation, the bare disk snapshot is just like saving the disk state when loosing power, not that bad, right? > A better alternative would be a live snapshot within qcow2. I think Kevin > has some good ideas about how to do this with qcow2 today but provided we > had a nice interface to do this, the changes to the live migration code > should be fairly straight forward. Hi Kevin, any idea about it? Live snapshot is very useful. Do you already have ideas/plans about it? I want to take a look at it, make it live! > > Regards, > > Anthony Liguori > >