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Description of problem: The drv_snapshot command allows QEMU to create snapshots using qcow2 (and similar formats) and pivot the drive over to the new file. Externally managed storage (iSCSI, SAN, LVM, btrfs, etc) require the mgmt tool to create the snapshot. While in most cases, QEMU can carry on using the original file after the snapshot is created, a few use cases/types of storage may still require that QEMU pivot over to a new file after snapshot creation. Thus we need a QMP command to pivot the file for a VM's drive on the fly. Version-Release number of selected component (if applicable): qemu-kvm-0.12.1.2-2.130.el6 How reproducible: N/a Steps to Reproduce: 1. N/a 2. 3. Actual results: Expected results: Additional info:
I think it makes sense to add this new command, but given the current schedule for snapshot support, I would leave it at low priority for 6.1 or push to 6.2. Jes
This request was evaluated by Red Hat Product Management for inclusion in the current release of Red Hat Enterprise Linux. Because the affected component is not scheduled to be updated in the current release, Red Hat is unfortunately unable to address this request at this time. Red Hat invites you to ask your support representative to propose this request, if appropriate and relevant, in the next release of Red Hat Enterprise Linux. If you would like it considered as an exception in the current release, please ask your support representative.
This request was erroneously denied for the current release of Red Hat Enterprise Linux. The error has been fixed and this request has been re-proposed for the current release.
The more I think of this command, the more convinced I am it is the wrong approach to the problem. Allowing a process outside of QEMU to pivot a drive means we support outside created snapshots, but that is race prone and while it may work for qcow2, there could be file formats that include state once the snapshot is created. The real solution is more fine grained access to the snapshot process in the running QEMU.
Given all the discussions about snapshots, it is clear that the snapshot should be created by QEMU, so it doesn't make sense to provide an QMP pivot command.