Hello,
We had a rather unpleseant surprise while upgrading our production datacenters
to oVirt 4.0 => 4.1 (although I think this problem is not related to oVirt
4.1).
Some critical VMs simply refused to reboot without any particular error message
other than "VM failed to boot"
After a stressfull 2h of investigation, it turns out that the problematic VMs
shared the same "exotic" condition. They were not rebooted since the latest
major upgrade 3.6 => 4.0 (I know, this is not a good practise and we
underestimated it's priority, we will change our reboot policies)
Their "custom compatilibity setting" was set to 3.6 !! When changing this
setting to "Empty", The VM booted normaly. Hard to find, easy to fix !! ;)
Neverthess, there is little to none information/documentation about the
usefullness of this setting, and I have a hard time understanding the
consequences of changing it manually.
Our oVirt datacenter (which has engine 4.1.1, but some hosts on 4.0, so it's
still on 4.0 compatibility) hosts currently +- 200 Vms,
- 10 with "custom compatilibity setting" set to 3.6 - which will not (reb)boot
in current state,
- 30some with "custom compatilibity setting" set to 4.0 - which (re)boot
normally
- the rest with "custom compatilibity setting" set to "empty" - which (re)boot
normally
So can a oVirt guru please answer the following questions :
- What does this setting do? which are the consequences of changing it manually
?
- Is it "normal" that a VM not reboooted since the 3.6 update does not boot if
a new major upgrade is done on hostig host ? (maybe a exotic bug worth
correcting ?)
- Which are the possible consequences of manually setting this setting to
"Empty" in all my VMs (running or stopped) ?
- Which events will change this setting automatically ? (cluster major version
upgrade, first reboot after upgrade, ...) ?
- Some of my VMs have custom_compatibility_version set to 4.0 (in REST API)
eventough they have been recently rebooted and "custom compatilibity setting"
is empty in GUI, who's this possible ?
cordialement, regards,
Nelson LAMEIRAS
Ingénieur Systèmes et Réseaux / Systems and Networks engineer
Tel: +33 5 32 09 09 70
nelson.lamei...@lyra-network.com
www.lyra-network.com | www.payzen.eu
Lyra Network, 109 rue de l'innovation, 31670 Labège, FRANCE
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