[CLOUDSTACK-732] Add back KVM snapshot support

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Invalid
• Affects Version/s: 4.0.0
• Fix Version/s: 4.2.1
• Component/s: KVM
• Security Level: Public (Anyone can view this level - this is the default.)
• Environment: RHEL 6.3
• Assignee: Disheng Su
• Reporter: Disheng Su
• Due: 31/Jan/13
• Created: 03/Jan/13 20:09
• Updated: 22/Oct/13 21:25
• Resolved: 16/Oct/13 05:01

Description

In the latest KVM(on both RHEL 6.3 and Ubuntu 12.04), it supports external snapshot. We need to investigate the status of external snapshot, as far as I know, it still doesn't support disk-only snapshot(taking snapshot will pause VM for a long time, e.g. few minutes).
1. testing external snapshot: take an external snapshot instead of default qcow2 internal snapshot, then back it up into backup storage. Only need to test with libvirt snapshot API, if it works, then works, no need to hack on the qemu-kvm.
2. test how long it will pause a VM during taking snapshot. from link [2] and [3], only qemu-kvm-rhev supports disk-only snapshot, not sure ubuntu 12.04 supports it or not. We need to investigate on the issue.

If item 1 and item 2(disk-only snapshot) works, then we can support default kvm qcow2 snapshot again.

The link:
[1] http://kashyapc.wordpress.com/2011/10/04/snapshotting-with-libvirt-for-qcow2-images/
[2] http://www.linux-kvm.com/content/first-look-virtual-machine-online-disk-snapshots-coming-fedora-18
[3] http://www.redhat.com/archives/libvir-list/2012-July/msg00782.html