[ovirt-users] ovirt 3.5 and power outages

[Olivier Navas]

Hi !

As you pointed, it wouldn't be safe if ovirt only tried to communicate with the host.

This is why Ovirt (and other cluster software) include a way to power cycle hosts. If host is not responding, for any reason (software or hardware failure), before cluster migrates vms, host will be fenced (power off and on again) by an other host in the cluster.

You need some special hardware to manage power cycling, and you need to configure it on "power management" section of host parameters.

On the HP servers we use, we can configure ILO as power management method. This way, Ovirt can control power of the hosts as if we used the server web interface to power cycle the server. It works very well for us (since ovirt 3.4 or 3.5) and does not require some additional hardware, but I think it will not work if a hardware failure has an impact on ILO hardware (don't know if it may happen).

You also can add some specific hardware to manage power supplies. I used to buy APC masterswitch (replaced by apc AP7900) for this purpose, but this requires some additional hardware and is not as convenient as ILO (IMHO).

In both cases, you have to ensure that you always provide power to your servers, your switches, and your power management hardware with dual power supplies, connected to different power lines, different UPS, and so on because if a single power failure can turn off both your server and your power cycle mechanism, then Ovirt won't be able to recover.




----- Mail original -----
> De: "Kostyrev Aleksandr" <kostyrev at tutu.ru>
> À: users at ovirt.org
> Envoyé: Dimanche 18 Janvier 2015 11:17:27
> Objet: [ovirt-users] ovirt 3.5 and power outages
> 
> good day, everybody!
> I've got three node cluster with power management enabled.
> 
> As far as I understood to restart vms on the other host in the cluster
> in case when host suffered from power outage
> the engine has to be able to connect to host (specifically to vdsm) to
> be sure that host has been rebooted and it's not running any vms.
> 
> But what if I'm running a lot of vms on the host and it's 3 o'clock in
> the morning and
> 1) engine has rebooted the host but the host cannot boot because of some
> hardware problem or new kernel gives a kernel panic?
> 2) the host's motherboard burned out and it cannot get booted
> 
> so the engine will never connect to host and therefore all the vms that
> were running on that host won't migrate to other node in the cluster.
> So my cluster in that case is useless 'cause I'm not there to press
> "confirm host has been rebooted'.
> 
> --
> С уважением,
> Костырев Александр,
> системный администратор
> _______________________________________________
> Users mailing list
> Users at ovirt.org
> http://lists.ovirt.org/mailman/listinfo/users
> 

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