[ovirt-users] Fake power management?

[Barak Azulay]

----- Original Message -----
> From: "mots" <mots at nepu.moe>
> To: "Barak Azulay" <bazulay at redhat.com>
> Cc: users at ovirt.org
> Sent: Tuesday, November 18, 2014 1:17:49 AM
> Subject: AW: [ovirt-users] Fake power management?
> 
> -----Ursprüngliche Nachricht-----
> 
> > Von:Barak Azulay <bazulay at redhat.com <mailto:bazulay at redhat.com> >
> > Gesendet: Mon 17 November 2014 23:30
> > An: Patrick Lottenbach <pl at a-bot.ch <mailto:pl at a-bot.ch> >
> > CC: users at ovirt.org <mailto:users at ovirt.org>
> > Betreff: Re: AW: [ovirt-users] Fake power management?
> > 
> > Well you can hack the solution in the form of replacing the fencing master
> > script to always return success (Eli can help you with that),
> > and define an imaginary fencing device on each host ... meaning that the
> > fencing command will always succeeds.
> > 
> 
> This sounds interesting. It's exactly what I need.
> 
> > But this may be risky ... as you might end up with the same VM running on 2
> > hosts.
> 
> As I see it, this would only happen if someone unplugs the network interface.
> I know this is a way to break the cluster. If someone unplugs the interface,
> then everything gets started twice anyways thanks to pacemaker being
> configured to ignore the lack of quorum and it would look silly in front of
> the customer.
> 
> > And one last note ... when you disconnect one of the hosts in the demo you
> > mentioned, I think you'll be better to disconnect the host that does not
> > run the engine ...
>  
> It just gets restarted on the remaining node and resumes operation. It even
> remembers which guests ran on which host.
> That part is really safe. The storage is configured to only report data as
> written when the write operation has finished on all (currently online)
> nodes, disk write caches are turned off in lvm.conf. PostreSQL is resilient
> enough to survive a crash like this.
> 
> Or am I missing something that might break?

Let me know if we missed something 
This is an interesting demo ;-)

> 
> > Barak
> 
> mots
> 
> > 
> > ----- Original Message -----
> > > From: "mots" <mots at nepu.moe <mailto:mots at nepu.moe> >
> > > To: "Barak Azulay" <bazulay at redhat.com <mailto:bazulay at redhat.com> >
> > > Cc: users at ovirt.org <mailto:users at ovirt.org>
> > > Sent: Monday, November 17, 2014 12:58:20 PM
> > > Subject: AW: [ovirt-users] Fake power management?
> > > 
> > > Yes, pacemaker manages the engine. That part is working fine, the engine
> > > restarts on the remaining node without problems.
> > > It's just that the guests don't come back up until the powered down node
> > > has
> > > been fenced manually.
> > > 
> > > -----Ursprüngliche Nachricht-----
> > > > Von:Barak Azulay <bazulay at redhat.com <mailto:bazulay at redhat.com>
> > > > <mailto:bazulay at redhat.com <mailto:bazulay at redhat.com> > >
> > > > Gesendet: Mon 17 November 2014 11:35
> > > > An: Patrick Lottenbach <pl at a-bot.ch <mailto:pl at a-bot.ch>
> > > > <mailto:pl at a-bot.ch <mailto:pl at a-bot.ch> > >
> > > > CC: users at ovirt.org <mailto:users at ovirt.org>  <mailto:users at ovirt.org
> > > > <mailto:users at ovirt.org> >
> > > > Betreff: Re: [ovirt-users] Fake power management?
> > > > 
> > > > 
> > > > 
> > > > ----- Original Message -----
> > > > > From: "mots" <mots at nepu.moe <mailto:mots at nepu.moe>
> > > > > <mailto:mots at nepu.moe <mailto:mots at nepu.moe> > >
> > > > > To: users at ovirt.org <mailto:users at ovirt.org>  <mailto:users at ovirt.org
> > > > > <mailto:users at ovirt.org> >
> > > > > Sent: Friday, November 14, 2014 4:54:08 PM
> > > > > Subject: [ovirt-users] Fake power management?
> > > > > 
> > > > > Fake power management? Hello,
> > > > > 
> > > > > I'm building a small demonstration system for our sales team to take
> > > > > to a
> > > > > customer so that they can show them our solutions.
> > > > > Hardware: Two Intel NUC's, a 4 port switch and a laptop.
> > > > > Engine: Runs as a VM on one of the NUCs, which one it runs on is
> > > > > determined
> > > > > by pacemaker.
> > > > > Storage: Also managed by pacemaker, it's drbd backed and accessed
> > > > > with
> > > > > iscsi.
> > > > > oVirt version: 3.5
> > > > > OS: CentOS 6.6
> > > > > 
> > > > > The idea is to have our sales representative (or the potential
> > > > > customer
> > > > > himself) randomly pull the plug on one of the NUCs to show that the
> > > > > system
> > > > > stays operational when part of the hardware fails.
> > > > 
> > > > I assume you are aware that the engine might fence the node it is
> > > > running
> > > > on ...
> > > > Or do you use pacemaker to run the engine as well ?
> > > > 
> > > > > My problem is that I don't have any way to implement power
> > > > > management, so
> > > > > the
> > > > > Engine can't fence nodes and won't restart guests that were running
> > > > > on
> > > > > the
> > > > > node which lost power. In pacemaker I can just configure fencing over
> > > > > SSH
> > > > > or
> > > > > even disable the requirement to do so completely. Is there something
> > > > > similar
> > > > > for oVirt, so that the Engine will consider a node which it can't
> > > > > connect
> > > > > to
> > > > > to be powered down?
> > > > > 
> > > > > Regards,
> > > > > 
> > > > > mots
> > > > > 
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> > > > > 
> > > > 
> > > 
> > >
> > 
> 
>