[Users] HA

[Michal Skrivanek]

On 4 Apr 2014, at 15:14, Sander Grendelman wrote:

> Do you have power management configured?
> Was the "failed" host fenced/rebooted?
> 
> 
> On Fri, Apr 4, 2014 at 2:21 PM, Koen Vanoppen <vanoppen.koen at gmail.com> wrote:
> So... It is possible for a fully automatic migration of the VM to another hypervisor in case Storage connection fails?
> How can we make this happen? Because for the moment, when we tested the situation they stayed in pause state.
> (Test situation:
> Unplug the 2 fibre cables from the hypervisor
> VM's go in pause state
> VM's stayed in pause state until the failure was solved

as said before, it's not safe hence we (try to) not migrate them.
They only get paused when they actually access the storage which may not be always the case. I.e. the storage connection is severed, host deemed NonOperational and VMs are getting migrated from it, then some of them will succeed if they didn't access that "bad" storage … the paused VMs will remain (mostly, it can still happen that they appear paused migrated on other host when the disk access occurs only at the last stage of migration)


so in other words, if you want to migrate the VMs without interruption it's not sometimes possible
if you are fine with the VMs restarted in short time on other host then power management/fencing will help here

Thanks,
michal
> )
> 
> 
> 
> They only returned when we restored the fiber connection to the Hypervisor…

yes, since 3.3 we have the autoresume feature

Thanks,
michal


> 
> Kind Regards,
> 
> Koen
> 
> 
> 
> 2014-04-04 13:52 GMT+02:00 Koen Vanoppen <vanoppen.koen at gmail.com>:
> So... It is possible for a fully automatic migration of the VM to another hypervisor in case Storage connection fails?
> How can we make this happen? Because for the moment, when we tested the situation they stayed in pause state.
> (Test situation:
> Unplug the 2 fibre cables from the hypervisor
> VM's go in pause state
> VM's stayed in pause state until the failure was solved
> )
> 
> 
> 
> They only returned when we restored the fiber connection to the Hypervisor...
> 
> Kind Regards,
> 
> Koen
> 
> 
> 2014-04-03 16:53 GMT+02:00 Koen Vanoppen <vanoppen.koen at gmail.com>:
> 
> ---------- Forwarded message ----------
> From: "Doron Fediuck" <dfediuck at redhat.com>
> Date: Apr 3, 2014 4:51 PM
> Subject: Re: [Users] HA
> To: "Koen Vanoppen" <vanoppen.koen at gmail.com>
> Cc: "Omer Frenkel" <ofrenkel at redhat.com>, <users at ovirt.org>, "Federico Simoncelli" <fsimonce at redhat.com>, "Allon Mureinik" <amureini at redhat.com>
> 
> 
> 
> ----- Original Message -----
> > From: "Koen Vanoppen" <vanoppen.koen at gmail.com>
> > To: "Omer Frenkel" <ofrenkel at redhat.com>, users at ovirt.org
> > Sent: Wednesday, April 2, 2014 4:17:36 PM
> > Subject: Re: [Users] HA
> >
> > Yes, indeed. I meant not-operational. Sorry.
> > So, if I understand this correctly. When we ever come in a situation that we
> > loose both storage connections on our hypervisor, we will have to manually
> > restore the connections first?
> >
> > And thanx for the tip for speeding up thins :-).
> >
> > Kind regards,
> >
> > Koen
> >
> >
> > 2014-04-02 15:14 GMT+02:00 Omer Frenkel < ofrenkel at redhat.com > :
> >
> >
> >
> >
> >
> > ----- Original Message -----
> > > From: "Koen Vanoppen" < vanoppen.koen at gmail.com >
> > > To: users at ovirt.org
> > > Sent: Wednesday, April 2, 2014 4:07:19 PM
> > > Subject: [Users] HA
> > >
> > > Dear All,
> > >
> > > Due our acceptance testing, we discovered something. (Document will
> > > follow).
> > > When we disable one fiber path, no problem multipath finds it way no pings
> > > are lost.
> > > BUT when we disabled both the fiber paths (so one of the storage domain is
> > > gone on this host, but still available on the other host), vms go in paused
> > > mode... He chooses a new SPM (can we speed this up?), put's the host in
> > > non-responsive (can we speed this up, more important) and the VM's stay on
> > > Paused mode... I would expect that they would be migrated (yes, HA is
> >
> > i guess you mean the host moves to not-operational (in contrast to
> > non-responsive)?
> > if so, the engine will not migrate vms that are paused to do io error,
> > because of data corruption risk.
> >
> > to speed up you can look at the storage domain monitoring timeout:
> > engine-config --get StorageDomainFalureTimeoutInMinutes
> >
> >
> > > enabled) to the other host and reboot there... Any solution? We are still
> > > using oVirt 3.3.1 , but we are planning a upgrade to 3.4 after the easter
> > > holiday.
> > >
> > > Kind Regards,
> > >
> > > Koen
> > >
> 
> Hi Koen,
> Resuming from paused due to io issues is supported (adding relevant folks).
> Regardless, if you did not define power management, you should manually approve
> source host was rebooted in order for migration to proceed. Otherwise we risk
> split-brain scenario.
> 
> Doron
> 
> 
> 
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