Re: [libvirt-users] KVM incremental backup using CBT

On Fri, Oct 10, 2014 at 07:32:06PM -0600, Eric Blake wrote: > On 10/10/2014 11:37 AM, Jd wrote: >> Hi >> Looking in to implementing (CBT like) delta backup for KVM. > Not quite sure what you mean by CBT. > >> The following looks promising..(last paragraph) >> http://wiki.qemu.org/Features/Snapshots2 >> > Libvirt hasn't yet been patched to take advantage of all the latest qemu > features. Patches are welcome. But libvirt already knows how to create > external snapshots and do blockpull (backing files pulled into the > active image so the backing isn't needed any more) and commit (active > files pushed into the backing files), and even though it is not as > full-featured as where we'd like to get, it can already do quite a bit. To expand an example of what Eric wrote here about external snapshots, some commands to try: 1. Check the current acitve disk image in use: $ virsh domblklist vm1 2. Create an external live snapshot: $ virsh snapshot-create-as --domain vm1 sn1 \ --diskspec vda,file=/export/images/sn1.qcow2 \ --disk-only --atomic --no-metadata Note (thanks Eric Blake): Above, if you have QEMU guest agent installed in your virtual machine, try --quiesce option with 'snapshot-create-as' to ensure you have a consistent disk state. Now, you have a disk image chain: base <-sn1 (live QEMU) 3. Take a backup of the original disk in backround: $ rsync -avh --progress /export/images/base.img \ /export/images/copy.img 4. Commit the sn1 contents back into base: $ virsh blockcommit vm1 vda --active --verbose --pivot Now, the chain is: base (live QEMU) with contents from sn1 live committed into base. 5. Check the current acitve disk image in use again: $ virsh domblklist vm1