Bug 1158974

Summary:	live snapshot not supported if VDSM does not report the status
Product:	[Retired] oVirt	Reporter:	Francesco Romani <fromani>
Component:	ovirt-engine-core	Assignee:	Francesco Romani <fromani>
Status:	CLOSED DUPLICATE	QA Contact:	Pavel Stehlik <pstehlik>
Severity:	medium	Docs Contact:
Priority:	high
Version:	3.5	CC:	ecohen, gklein, iheim, lsurette, ofrenkel, rbalakri, yeylon
Target Milestone:	---
Target Release:	3.5.1
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:	virt
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2014-11-03 07:31:44 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	Virt	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:
Bug Blocks:	1155170

Description Francesco Romani 2014-10-30 15:38:24 UTC

Description of problem:
Certain QEMU does not support live snapshotting.
VDSM, through libvirt, report this capability to Engine, which reports back to the user in the Host tab, and inhibit the functionality if QEMU lacks it.

If live snapshot reporting is missing, Engine assumes it is supported and works as usual for backward compatibility.

Unfortunately, one sequence of events is not covered
- VDSM reports live snapshot as disabled
- libvirt is updated (https://bugzilla.redhat.com/show_bug.cgi?id=1149667)
  and stops to report the capability. This makes VDSM stop reporting as well
- Engine no longer updates its tables, so it is stuck with old value
- live snapshot is gone without good reason

Mitigation:
apply libvirt update before to add any host

Workaround:
After libvirt is updated, with Engine shutoff,
update DB table

update vds_dynamic set is_live_snapshot_support='true'  -- for all affected hosts

Version-Release number of selected component (if applicable):
3.5.0

How reproducible:
100% (estimated)

Steps to Reproduce:
see description above

Actual results:
Live snapshot support still reported as disabled

Expected results:
Live snapshot support available again

Comment 1 Francesco Romani 2014-10-30 22:49:34 UTC

severity medium due to not so common scenario: user need to add host to Engine with buggy libvirt, then update libvirt to hit the bug and due to availability of simple workaround.

Comment 2 Francesco Romani 2014-11-03 07:31:44 UTC

More streamlined process on 1159221

*** This bug has been marked as a duplicate of bug 1159211 ***