[drbd-mc] Some VMs ignored by drbd-mc - strange recovery

Whit Blauvelt whit.drbd at transpect.com
Mon Sep 5 14:47:01 CEST 2011

On Mon, Sep 05, 2011 at 01:46:54PM +0200, Rasto Levrinc wrote:
> On Thu, Sep 1, 2011 at 5:47 PM, Whit Blauvelt <whit.drbd at transpect.com> wrote:
> > After confirming that 0.9.4 and 0.9.5 had the same problem with showing all
> > the VMs as 0.9.7, I was logged into a different VM by ssh (called "geos_x")
> > - not on a DRBD resource in this case, but drbd-mc had recognized it as
> > existing. In the ssh session I did a shutdown. I also had a console opened
> > into it via drbd-mc at the time, and the VMs list open in drbd-mc.
> >
> > On shutting down geos_x, drbd-mc blinked a number of times, and finally
> > stabilized with the "missing" VMs showing in the VMs list.
> >
> > Okay, what's that about?

> first there can be some mix-up with uuids, like having the same uuid
> for different VMs across the cluster.

Just checked. Not the case.

> DRBD MC looks for the /etc/libvirt/qemu/*.xml to get a list of VMs. If
> you use sudo make sure the user can read this directory.

I don't use sudo. I do everything as root. 

> Then it calls e.g. "virsh dominfo geos3" and "virsh dumpxml geos3" to
> see if they are defined.

Of course they're defined. They're running! At this point drbd has, as I
mentioned above, rediscovered them. But they were running the whole time,
and fully available to normal operations through virsh - as they still are.

> you can also try to execute "/usr/local/bin/drbd-gui-helper-0.9.7
> get-vm-info" on all cluster nodes to see what is going on.

Nice script. But it's just calling virsh, isn't it? So since virsh has had
no problem, where drbd-mc has, how will that diagnose drbd-mc's problem?

I do like drbd-mc, a lot. Just wanted you to know about the bug.


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