Re: [Xen-devel] Xen blktap driver for Ceph RBD : Anybody wants to test ? :p

[James Harper <james.harper@xxxxxxxxxxxxxxxx>]

> >
> > Hi,
> >
> > > I just tested with tap2:aio and that worked (had an old image of the VM
> on
> > lvm still so just tested with that). Switching back to rbd and it crashes 
> > every
> > time, just as postgres is starting in the vm. Booting into single user mode,
> > waiting 30 seconds, then letting the boot continue it still crashes at the
> same
> > point so I think it's not a timing thing - maybe postgres has a disk access
> > pattern that is triggering the bug?
> >
> > Mmm, that's really interesting.
> >
> > Could you try to disable request merging ? Just give option
> > max_merge_size=0 in the tap2 disk description. Something like
> > 'tap2:tapdisk:rbd:rbd/test:max_merge_size=0,xvda2,w'
> >
> 
> Just as suddenly the problem went away and I can no longer reproduce the
> crash on startup. Very frustrating. Most likely it still crashed during heavy 
> use
> but that can take days.
> 
> I've just upgraded librbd to dumpling (from cuttlefish) on that one server and
> will see what it's doing by morning. I'll disable merging when I can reproduce
> it next.
> 

I just had a crash since upgrading to dumpling, and will disable merging 
tonight.

James

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