On 04/13/2012 10:23 AM, Paolo Bonzini wrote: > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > docs/live-block-ops.txt | 38 +++++++++++++++++++++++++++++++------- > 1 file changed, 31 insertions(+), 7 deletions(-) >
> > +Live block migration > +==================== > + > +Migrating an in use image to another destination in the filesystem > +is done through image mirroring. The idea is to execute > +'drive_mirror virtio0 /new-path/disk.img qcow2' while the guest > +is running. The topmost image ([D] in the example above) will > +be copied to the given path, and the two can be kept in sync. > + > +Progress can be monitored using 'info block-jobs'. Once this command > +reports something like maybe: s/reports something like/reports completion equal to size, as in/ > + > + Type mirror, device virtio0: Completed 1048576000 of 1048576000 bytes > + > +it is possible to switch to the destination using > + > +(qemu) drive_reopen virtio0 /new-path/disk.img > + > +This assumes that all images A/B/C are also present under /new-path > +or. An image can be omitted from the destination if one of the images Dangling sentence. > +refers to its backing file using an absolute path. I think you need to rework this paragraph. It sounds like you are trying to state whether /new-path/disk.img will have an absolute backing file path (in which case, it is reusing C, and therefore A and B, from the same locations found when originally opening D), or whether /new-path/disk.img will have a relative backing path (this would be either through a relative-paths mode option, or through the reuse of an existing file intentionally created with a relative backing path), in which case the reopen now resolves the backing path locally so A, B, and C must all be present at /new-path for the reopen to succeed. > + > + > Live block copy > =============== > > To copy an in use image to another destination in the filesystem, one > -should create a live snapshot in the desired destination, then stream > -into that image. Example: > - > -(qemu) snapshot_blkdev ide0-hd0 /new-path/disk.img qcow2 > +can also use mirroring with the -f option. > > -(qemu) block_stream ide0-hd0 > +(qemu) drive_mirror -f virtio0 /new-path/disk.img qcow2 > > +Note that if one image in the chain is in raw format, the > +resulting copy might not be thin-provisioned anymore, depending on > +the underlying file system. > > +It is also possible to use raw as the format of the destination image. > +Converting an image to raw will properly support thin provisioning. Do you need to mention the use of block_job_cancel needed at the point where you are ready to stop qemu from writing into the copy? -- Eric Blake ebl...@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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