[ovirt-users] Can we debug some truths/myths/facts about hosted-engine and gluster?

[Jason Brooks]

----- Original Message -----
> From: "Jason Brooks" <jbrooks at redhat.com>
> To: "Andrew Lau" <andrew at andrewklau.com>
> Cc: "users" <users at ovirt.org>
> Sent: Tuesday, July 22, 2014 8:29:46 AM
> Subject: Re: [ovirt-users] Can we debug some truths/myths/facts	about	hosted-engine and gluster?
> 
> 
> 
> ----- Original Message -----
> > From: "Andrew Lau" <andrew at andrewklau.com>
> > To: "users" <users at ovirt.org>
> > Sent: Friday, July 18, 2014 4:50:31 AM
> > Subject: [ovirt-users] Can we debug some truths/myths/facts about
> > 	hosted-engine and gluster?
> > 
> > Hi all,
> > 
> > As most of you have got hints from previous messages, hosted engine won't
> > work on gluster . A quote from BZ1097639
> > 
> > "Using hosted engine with Gluster backed storage is currently something we
> > really warn against.
> 
> My current setup is hosted engine, configured w/ gluster storage as described
> in my
> blog post, but with three hosts and replica 3 volumes.
> 
> Only issue I've seen is an errant message about the Hosted Engine being down
> following an engine migration. The engine does migrate successfully, though.
> 
> RE your bug, what do you use for a mount point for the nfs storage?

In the log you attached to your bug, it looks like you're using localhost as
the nfs mount point. I use a dns name that resolves to the virtual IP hosted
by ctdb. So, you're only ever talking to one nfs server at a time, and failover
between the nfs hosts is handled by ctdb.

Anyway, like I said, my main testing rig is now using this configuration, 
help me try and break it. :)

> 
> Jason
> 
> 
> > 
> > 
> > I think this bug should be closed or re-targeted at documentation,
> > because there is nothing we can do here. Hosted engine assumes that
> > all writes are atomic and (immediately) available for all hosts in the
> > cluster. Gluster violates those assumptions.
> > 
> > ​"
> > 
> > ​Until the documentation gets updated, I hope this serves as a useful
> > notice at least to save people some of the headaches I hit like
> > hosted-engine starting up multiple VMs because of above issue.
> > ​
> > 
> > Now my question, does this theory prevent a scenario of perhaps something
> > like a gluster replicated volume being mounted as a glusterfs filesystem
> > and then re-exported as the native kernel NFS share for the hosted-engine
> > to consume? It could then be possible to chuck ctdb in there to provide a
> > last resort failover solution. I have tried myself and suggested it to two
> > people who are running a similar setup. Now using the native kernel NFS
> > server for hosted-engine and they haven't reported as many issues. Curious,
> > could anyone validate my theory on this?
> > 
> > Thanks,
> > Andrew
> > 
> > _______________________________________________
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> > Users at ovirt.org
> > http://lists.ovirt.org/mailman/listinfo/users
> > 
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