Snapshot/rollback in Kvm using DRBD

drbdhigh-availabilitykvm-virtualizationlibvirt

I want to use the HA on a virtual machine on two server using KVM/libvirt.

I placed the image on a partition using DRBD.

I'm using the qcow2 format and i'm taking the snapshot, using virsh snapshot-create vm

I think that it saves it in the qcow2 image. But it creates the xml doc in the /var/lib/libvirt/qemu/snapshot/vm/1306756846.xml. When an host crushes, the other server is not able to see the snapshot unless i copy the snapshot file.

It is also possible to consolidate snapshot?

Best Answer

I believe the XML file is just something virsh creates for the own bookkeeping and thus redundant.

You should be able to see the snapshot information in the qcow2 file using the qemu-img info <filename> command and revert to them using qemu-img snapshot -a <snapshot-name> <filename>.

Edit: according to the docs, a memory snapshot should have been created as well when using virsh create-snapshot. I have no idea where this one is going, but if you want more than just disk states, you should take care of the XML file to be copied as well - maybe by creating a symlink for /var/lib/libvirt/qemu/snapshot/vm/ to point at a directory in your DRBD-replicated volume.

Related Solutions

Linux – mount qcow2 snapshots

You should apply the snapshot and mount the image like always. It's better to create a snapshot right before applying if you want to turn back to the original disk contents before you do these operations. After you apply the snapshot you just mount the image with qemu-nbd as always:

# modprobe nbd max_part=8
$ qemu-img snapshot -c backup image.qcow2
$ qemu-img snapshot -a old_snapshot image.qcow2
$ qemu-nbd --connect=/dev/nbd0 image.qcow2
# mount /dev/nbd0p1 /mnt

You might want to save snapshot separately and mount it as another disk drive. For this you should use convert comand for qemu-img.

$ qemu-img convert -s old_snapshot image.qcow2 old_snapshot.qcow2
$ qemu-nbd --connect=/dev/nbd0 old_snapshot.qcow2
# mount /dev/nbd0p1 /mnt

See man qemu-img(1) and qemu-nbd(1) for more details.

Libvirt qemu/kvm migration problem

Make sure you have TCP 49152-49261 open between the hosts and the hostnames for each in either DNS or each other's /etc/hosts files. For some reason KVM migration works off of hostname rather than IP address.

Best Answer

Related Solutions

Linux – mount qcow2 snapshots

Libvirt qemu/kvm migration problem

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