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Re: [Qemu-devel] KVM call agenda for June 28
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] KVM call agenda for June 28 |
Date: |
Tue, 5 Jul 2011 09:58:58 -0300 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Tue, Jul 05, 2011 at 01:40:08PM +0100, Stefan Hajnoczi wrote:
> On Tue, Jul 5, 2011 at 9:01 AM, Dor Laor <address@hidden> wrote:
> > I tried to re-arrange all of the requirements and use cases using this wiki
> > page: http://wiki.qemu.org/Features/LiveBlockMigration
> >
> > It would be the best to agree upon the most interesting use cases (while we
> > make sure we cover future ones) and agree to them.
> > The next step is to set the interface for all the various verbs since the
> > implementation seems to be converging.
>
> Live block copy was supposed to support snapshot merge. I think the
> current favored approach is to make the source image a backing file to
> the destination image and essentially do image streaming.
>
> Using this mechanism for snapshot merge is tricky. The COW file
> already uses the read-only snapshot base image. So now we cannot
> trivally copy the COW file contents back into the snapshot base image
> using live block copy.
It never did. Live copy creates a new image were both snapshot and
"current" are copied to.
This is similar with image streaming.
> It seems like snapshot merge will require dedicated code that reads
> the allocated clusters from the COW file and writes them back into the
> base image.
>
> A very inefficient alternative would be to create a third image, the
> "merge" image file, which has the COW file as its backing file:
> snapshot (base) -> cow -> merge
>
> All data from snapshot and cow is copied into merge and then snapshot
> and cow can be deleted. But this approach is results in full data
> copying and uses potentially 3x space if cow is close to the size of
> snapshot.
Management can set a higher limit on the size of data that is merged,
and create a new base once exceeded. This avoids copying excessive
amounts of data.
> Any other ideas that reuse live block copy for snapshot merge?
>
> Stefan
- Re: [Qemu-devel] KVM call agenda for June 28, Dor Laor, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28,
Marcelo Tosatti <=
- Re: [Qemu-devel] KVM call agenda for June 28, Dor Laor, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Kevin Wolf, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Dor Laor, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/07/05
- Re: [Qemu-devel] KVM call agenda for June 28, Kevin Wolf, 2011/07/06
- Re: [Qemu-devel] KVM call agenda for June 28, Stefan Hajnoczi, 2011/07/07
- Re: [Qemu-devel] KVM call agenda for June 28, Marcelo Tosatti, 2011/07/07