Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> --- docs/live-block-ops.txt | 38 +++++++++++++++++++++++++++++++------- 1 file changed, 31 insertions(+), 7 deletions(-)
diff --git a/docs/live-block-ops.txt b/docs/live-block-ops.txt index a257087..caf3466 100644 --- a/docs/live-block-ops.txt +++ b/docs/live-block-ops.txt @@ -1,8 +1,7 @@ LIVE BLOCK OPERATIONS ===================== -High level description of live block operations. Note these are not -supported for use with the raw format at the moment. +High level description of live block operations. Snapshot live merge =================== @@ -44,15 +43,40 @@ In the example above, the command would be: (qemu) block_stream virtio0 A +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 + + 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 +refers to its backing file using an absolute path. + + 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. -- 1.7.9.3