[one-users] Questions about host & VM failover mechanisms

Tino Vazquez tinova at fdi.ucm.es
Tue Nov 10 03:48:38 PST 2009

Hi Ranga,

comments inline,

On Tue, Oct 27, 2009 at 6:41 PM, Rangababu Chakravarthula <
rbabu at hexagrid.com> wrote:

> Opennebula team,
> (a) What mechanism does Opennebula use to monitor hosts?

It sends probes (scripts) using ssh

> (b) I would like to know how we can migrate VM's in the following two
> scenarios.
> (1) The host might be up but due to some network issues, opennebula is not
> able to monitor the host.
>  (a) Does it move the host status to ERR?

Yep, but it keeps trying to monitor them

>  (b) What does it do to the VM's. Does it move to a different state?

No, it tries to connect to them.

>  (c) Is there a mechanism to automatically migrate those VM's to different
> host?

If the host is unreachable, this is tough to do.

> (2) When somebody manually shutdown the host. Vm's on that host are not
> accessible anymore for users.
> Is there a way during the shutdown sequence we can trigger a script to
> migrate the VM's ? Because, by the time opennebula
> finds that host is down users will get effected. How to address this?

This is tricky. If the physical host is shuttted down, there is virtually
not a lot you can do, appart from maybe starting the VMs again in another

> Thanks
> Ranga

Hope it helps,


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> Users at lists.opennebula.org
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Constantino Vázquez, Grid Technology Engineer/Researcher:
DSA Research Group: http://dsa-research.org
Globus GridWay Metascheduler: http://www.GridWay.org
OpenNebula Virtual Infrastructure Engine: http://www.OpenNebula.org
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