Some thoughts on enhancing High Availability in oVirt

[Lon Hohberger]

On 02/15/2012 06:12 AM, Livnat Peer wrote:

>>> HA is a simple use case of policy.
>>
>> *Today* HA is simply 'if VM is down restart it' but what Perry was suggesting was to improve this to something more robust.
>
> I think that the main concept of what Perry suggested (leaving the
> implementation details aside :)) is to add HA of services.

FYI - What we have in cluster today is simply an external monitor script 
to monitor something inside the VM (opaque).  This only moderately 
improves the availability of the application, since we still restart the 
VM to restart the application.

(Point of fact, this functionality was built specifically for 
RHEVM-in-VM deployments on bare-metal clusters)


> I like this idea and I would like to extend it a little bit.
> How about services that are spread on more than a single VM.
> I would like to be able to define a service and specify which VM/s
> provides this service and add HA flag on the service.

This sounds like Pacemaker's 'clone' concept.  I don't know if Pacemaker 
Cloud supports this or not; Steve?


> Then i would like to manage policies around it - I define a service
> with 3 VMs providing this service and I want to have at least 2 VM
> running it at any given time. (now the VMs are not highly available only
> the service is.)

Sure, that's a natural extension.

-- Lon