Re: [Qemu-devel] live migration which includes previos snapshot

[Eric Blake <eblake@redhat.com>]

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On 11/02/2012 04:30 AM, Stefan Hajnoczi wrote:

> II. If you want to use internal snapshots in a single qcow2 file, you
> will need to modify QEMU code more:
> 1. Implement BlockDriverState snapshot slave support so a qcow2
> snapshot can be read-only accessed as a BlockDriverState while the
> master BlockDriverState for the image still writes into the image
> file.  This is mainly qcow2 refactoring and block.c glue code.

You are not the first to request this - libvirt would also like the
ability to have read-only access into the contents of an internal
snapshot while the rest of qemu continues to write into the image.

> 2. Use Paolo's runtime NBD server to export the snapshot slave when
> the VM is forked:

An NBD server on top of the read-only state is an additional step that
will make access easier.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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