[libvirt-users] KVM incremental backup using CBT
Jd
jd_jedi at convirture.com
Mon Oct 13 04:19:35 UTC 2014
Thanks Kashyap,
The command line examples makes thing quite clear :)
rsync for image (large) files create a new file for every little
change, that was the reason I started looking in to using dirty bitmaps.
/Jd
On 10/11/14, 1:13 AM, Kashyap Chamarthy wrote:
> 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
>
>
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