[DRBD-user] Kernel hung on DRBD / MD RAID

[Micha Kersloot]

Hi Andreas,

----- Oorspronkelijk bericht -----
> Van: "Andreas Bauer" <ab at voltage.de>
> Aan: drbd-user at lists.linbit.com, info at kovoks.nl
> Verzonden: Maandag 5 maart 2012 16:16:50
> Onderwerp: RE: [DRBD-user] Kernel hung on DRBD / MD RAID
> 
> From:	Micha Kersloot <micha at kovoks.nl>
> Sent:	Mon 05-03-2012 11:31
> 
> > Hi Andreas,
> > 
> > > > Looks like MD is stepping on it's own toes there.
> > >
> > > Stepping on one's own toes is something one isn't supposed to do,
> > > right? ;-)
> > >
> > > I might raise the issue with the MD developpers but at the moment
> > > I am still
> > confused why DRBD did
> > > behave like it did. How would DRBD behave when the backing device
> > > blocks hard?
> > 
> > did you get any further on this original problem as we are battling
> > the same
> > problems for some time now, but with a slightly different
> > configuration:
> > XEN (4.0.1) Virtual machines, on top of
> > DRBD (8.3.7)on top of
> > LVM2 on top of
> > RAID1 (pv=/dev/md3), on top of
> > sda4, sdb4
> 
> This looks pretty much the same as my configuration, albeit with XEN
> rather than KVM.
> 
> No I haven't gotten any further and do not have equipment for testing
> at the moment, but put my effort into carefully scheduling all
> cron-jobs / backups so that there are no RAID resync/verify runs
> when heavy I/O can be expected. So far no recurrence. By default MD
> resync runs first sunday each month, around 1am on Debian.

We've even disabled RAID1 on our production servers and fully rely on drbd because we are unable to schedule the load. We hoped converting to KVM could solve the problem because there is no separate hypervisor, but that is not the solution you say. 

We use all the different components (xen, drbd, raid1) for several years now in different combinations, but only this specific combination of components seem to have problems. I have no idea where to start debugging, or even where to start asking for help, do you have an idea?

Met vriendelijke groet,

Micha Kersloot

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