[ovirt-users] Fake power management?

[mots]

-----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?

> 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
> > > > 
> > > > _______________________________________________
> > > > Users mailing list
> > > > Users at ovirt.org <mailto:Users at ovirt.org>  <mailto:Users at ovirt.org <mailto:Users at ovirt.org> >
> > > > http://lists.ovirt.org/mailman/listinfo/users <http://lists.ovirt.org/mailman/listinfo/users> 
> > > > <" target="_blank">http://lists.ovirt.org/mailman/listinfo/users> <http://lists.ovirt.org/mailman/listinfo/users> ;
> > > > 
> > > 
> > 
> >
> 

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