Yes, bringing up both engines can cause disaster, iv'e tried that once to bring up both of my engines and my engine1 droped the connection coz host1 was called by the engine2, host1 don't know how to talk two engines at the same time, I tried this with a running vm on the host1 just to test if what will happen to that vm and the results are "the vm is lost in the space".



On Thu, Jun 16, 2016 at 3:13 PM, Michal Skrivanek <michal.skrivanek@redhat.com> wrote:

On 16 Jun 2016, at 09:07, Yaniv Kaul <ykaul@redhat.com> wrote:



On Thu, Jun 16, 2016 at 9:29 AM, Yedidyah Bar David <didi@redhat.com> wrote:
On Thu, Jun 16, 2016 at 9:10 AM, Yaniv Kaul <ykaul@redhat.com> wrote:
>
>
> On Thu, Jun 16, 2016 at 8:53 AM, Yedidyah Bar David <didi@redhat.com> wrote:
>>
>> On Thu, Jun 16, 2016 at 5:33 AM, Sandvik Agustin
>> <agustinsandvik@gmail.com> wrote:
>> > Hi users,
>> >
>> > Good day, is it possible to configure two ovirt-engine to manage one
>> > hypervisor? My purpose for this is what if the first ovirt-engine fails,
>> > I
>> > still have the 2nd ovirt-engine to manage hypervisor.
>> >
>> > is this possible? or any suggestion similar to my purpose?
>>
>> The "normal" solution is hosted-engine, which has HA - the engine
>> runs in a VM, and HA daemons monitor it and the hosts, and if there
>> is a problem they can start it on another host.
>>
>> There were discussions in the past, which you can find in the list
>> archives,
>> about running two engines against a single database, and current bottom
>> line
>> is that it's not supported, will not work, and iiuc will require some
>> significant development investment to support.
>>
>> You might manage to have an active/passive solution - install an engine
>> on two machines, configure both to use the same remote database, but
>> make sure only one of them is active at any given time. Not sure if that's
>> considered "fully supported", but might come close.

even when you make it work when cert issues are sorted out, you need to be very careful not to bring both engines up managing a same host, they will fight over it and the monitoring is going to be received only by one of the engines, which in turn may cause HA VMs restart and split brains all over the place.

>
>
> That's not enough - they need to share the same set of certificates...

Best is to simply clone the machine after initial setup then change
what's needed, or backup/restore only files (engine-backup --mode=backup
--scope=files).

Didn't check, but I do not think they actually need all the certs of
all hosts - that is, that it's not mandatory to keep /etc/pki synced
between them after initial setup. Didn't try that myself.

I'm not sure what happens when you provision a host from Mgmt A, then move to Mgmt B and provision another from it:
1. Mgmt A won't be aware of that host, from cert req perspective. May not be such a big deal - donno.
2. Can Mgmt A provision another host? Need to ensure the certificate serial numbers are OK, etc.

They really need to share the CA DB.
The backup-restore sounds like good approach  to me.
Y.


> Y.
>
>>
>>
>> You can find on the net docs/resources about creating a redundant
>> postgresql cluster.
>>
>> Best,
>> --
>> Didi
>> _______________________________________________
>> Users mailing list
>> Users@ovirt.org
>> http://lists.ovirt.org/mailman/listinfo/users
>
>



--
Didi

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