Hello Eric, From: Eric Blake <ebl...@redhat.com> Subject: Re: [Qemu-devel] live migration which includes previos snapshot Date: Fri, 02 Nov 2012 07:12:21 -0600
> 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. Do you mean that libvirt can change the access mode of internal harddisk from read-write to read-only? Please tell me how to change the mode by libvirt. Does the qemu which has read-only access only, use another COW file? Nested COWs sound interested, but the inter COW must be read-only, I think. > > 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. Does an NBD work as COW? It looks convenient. Thank you. ------ suzaki
