On 5/21/2014 11:15 AM, Giuseppe Ragusa wrote:
Hi,
> ----- Original Message -----
> > From: "Ted Miller" <tmiller at hcjb.org>
> > To: "users" <users at ovirt.org>
> > Sent: Tuesday, May 20, 2014 11:31:42 PM
> > Subject: [ovirt-users] sanlock + gluster recovery -- RFE
> >
> > As you are aware, there is an ongoing split-brain problem with running
> > sanlock on replicated gluster storage. Personally, I believe that this is
> > the 5th time that I have been bitten by this sanlock+gluster problem.
> >
> > I believe that the following are true (if not, my entire request is
probably
> > off base).
> >
> >
> > * ovirt uses sanlock in such a way that when the sanlock storage is
on a
> > replicated gluster file system, very small storage disruptions can
> > result in a gluster split-brain on the sanlock space
>
> Although this is possible (at the moment) we are working hard to avoid it.
> The hardest part here is to ensure that the gluster volume is properly
> configured.
>
> The suggested configuration for a volume to be used with ovirt is:
>
> Volume Name: (...)
> Type: Replicate
> Volume ID: (...)
> Status: Started
> Number of Bricks: 1 x 3 = 3
> Transport-type: tcp
> Bricks:
> (...three bricks...)
> Options Reconfigured:
> network.ping-timeout: 10
> cluster.quorum-type: auto
>
> The two options ping-timeout and quorum-type are really important.
>
> You would also need a build where this bug is fixed in order to avoid any
> chance of a split-brain:
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1066996
It seems that the aforementioned bug is peculiar to 3-bricks setups.
I understand that a 3-bricks setup can allow proper quorum formation
without resorting to "first-configured-brick-has-more-weight" convention
used with only 2 bricks and quorum "auto" (which makes one node "special",
so not properly any-single-fault tolerant).
But, since we are on ovirt-users, is there a similar suggested
configuration for a 2-hosts setup oVirt+GlusterFS with oVirt-side power
management properly configured and tested-working?
I mean a configuration where "any" host can go south and oVirt (through the
other one) fences it (forcibly powering it off with confirmation from IPMI
or similar) then restarts HA-marked vms that were running there, all the
while keeping the underlying GlusterFS-based storage domains responsive and
readable/writeable (maybe apart from a lapse between detected other-node
unresposiveness and confirmed fencing)?
Furthermore: is such a suggested configuration possible in a
self-hosted-engine scenario?
Regards,
Giuseppe
> > How did I get into this mess?
> >
> > ...
> >
> > What I would like to see in ovirt to help me (and others like me).
Alternates
> > listed in order from most desirable (automatic) to least desirable (set of
> > commands to type, with lots of variables to figure out).
>
> The real solution is to avoid the split-brain altogether. At the moment it
> seems that using the suggested configurations and the bug fix we shouldn't
> hit a split-brain.
>
> > 1. automagic recovery
> >
> > 2. recovery subcommand
> >
> > 3. script
> >
> > 4. commands
>
> I think that the commands to resolve a split-brain should be documented.
> I just started a page here:
>
> http://www.ovirt.org/Gluster_Storage_Domain_Reference
I suggest you add these lines to the Gluster configuration, as I have seen
this come up multiple times on the User list:
storage.owner-uid: 36
storage.owner-gid: 36
Ted Miller
Elkhart, IN, USA
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