hi!
im currently experimenting with image fleecing, using the copy-before-write
technique during blockdev-backup. So far, i was able to create full backups
using the following approach:
1) Create target backup and fleecing image with same size as original disk,
attach them to qemu:
> qemu-img create -f qcow2 /tmp/fleece.qcow2 5G
> qemu-img create -f qcow2 /tmp/backup.qcow2 5G
> blockdev-add driver=qcow2 node-name=fleecie
> file={"driver":"file","filename":"/tmp/fleece.qcow2"}
> blockdev-add driver=qcow2 node-name=backup-target-file
> file={"driver":"file","filename":"/tmp/backup.qcow2"}
2) Create a persistent bitmap
> block-dirty-bitmap-add node=drive-virtio0 name=bitmap persistent=true
3) Add a copy-before-write device, targeting the fleece image:
> blockdev-add driver=copy-before-write node-name=cbw file=drive-virtio0
> target=fleecie
4) Modify the qdev to point at the copy-before-write filter:
> qom-set path=/machine/peripheral/virtio0/virtio-backend property=drive
> value=cbw
5) Add an snapshot-access image with CBW as reference:
> blockdev-add driver=snapshot-access file=cbw node-name=snapshot-backup-source
6) Create a full backup:
> blockdev-backup device=snapshot-backup-source target=backup-target-file
> sync=full job-id=test
7) Cleanup and dettach all the images.
Now, if repeating the same process attempting to start an incremental backup
with "sync=incremental" and the bitmap parameter, the Backup will fail with:
> "Bitmap 'bitmap' could not be found"
Looking at the query-block output, the bitmap seems to be inactive (or not
available during CBW beeing active).
I think im missing some action at step 7, to handle the bitmap correctly in
order to be able to use it with a next incremental backup using a CBW filter.
Any kind of help is highly appreciated :-)
bye,
- michael
