Bug 671449

Summary:	RFE: Support a QMP command to pivot a drive on a VM over to a new file.
Product:	Red Hat Enterprise Linux 6	Reporter:	Daniel Berrangé <berrange>
Component:	qemu-kvm	Assignee:	Jes Sorensen <Jes.Sorensen>
Status:	CLOSED WONTFIX	QA Contact:	Virtualization Bugs <virt-bugs>
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	6.1	CC:	bsarathy, Jes.Sorensen, juzhang, mkenneth, virt-maint
Target Milestone:	rc	Keywords:	FutureFeature
Target Release:	---
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	Enhancement
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2011-08-29 13:57:27 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Bug Depends On:
Bug Blocks:	693510

Description Daniel Berrangé 2011-01-21 14:55:55 UTC

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:

Comment 2 Jes Sorensen 2011-01-24 08:41:32 UTC

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

Comment 3 RHEL Program Management 2011-02-01 05:44:59 UTC

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.

Comment 4 RHEL Program Management 2011-02-01 19:09:39 UTC

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.

Comment 6 Jes Sorensen 2011-07-19 07:24:19 UTC

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.

Comment 7 Jes Sorensen 2011-08-29 13:57:27 UTC

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.