[DRBD-user] "local disk flush failed with status -5" on LVM

Lars Ellenberg lars.ellenberg at linbit.com
Tue May 13 10:50:22 CEST 2008


On Sat, May 10, 2008 at 12:28:00PM +0200, Iustin Pop wrote:
> Philipp Reisner wrote:
> > Am Sonntag, 4. Mai 2008 02:19:12 schrieb Wolfgang Denk:
> > > Hi,
> > >
> > > I'm trying to run DRBD on top of a LV, and get flooded with above
> > > error messages. I know this has been discussed before, see threads
> > > starting at
> > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008665.html
> > > and
> > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008519.html
> > >
> > > When this was discussed in February, it sounded (at least to me) as is
> > > a fix was on the way, see
> > > http://lists.linbit.com/pipermail/drbd-user/2008-February/008692.html
> > >
> > > However, even top of tree from the git repo still shows the same
> > > behaviour.
> > >
> > > Am I missing something, or is this usage mode so exotic  that  nobody
> > > cares?
> > >
> > 
> > Hi Wolfgang,
> > 
> > That is actually a kernel bug, I think in 2.6.24. Was fixed later, do not
> > know by heart with which "sucker" release. I guess it is fixed in 2.6.25.
> > 
> > Starting with 8.0.12 we offer a workaround for this in DRBD (and 8.2.6 
> > when I finally find the time to finish it):
> > 
> >   Add no-disk-flushes and no-md-flushes to your disk config.
> 
> Because this happens not only with LVM, but with any I/O subsystem that
> returns wrong error codes from flushes (e.g. broken scsi drivers or
> controller, I think), would it be a sane thing to disable barriers
> automatically if there after a certain number of errors?
> 
> (Looking at the barrier flush code I see that only the drbd_receiver.c
> has code for auto-disabling in case of EOPNOTSUPP, but drbd_actlog and
> drbd_bitmap.c don't; maybe these too should have this).

hm?
I think we do have a retry-and-disable-barriers in those places too.

> The reason I propose this is because with many deployments on different
> machines it would be better to let it always enabled at startup and
> allow it to autodisable if it see EOPNOTSUPP

that is the way we do it.

> or too many other errors.

and that is what we don't.

> And people can't always track latest upstream kernel...

if they are stuck with a kernel where DRBD spits out too much
noise due to barrier requests throwing IO errors,
then they have to disable use of barriers in the drbd config.

-- 
: Lars Ellenberg                           http://www.linbit.com :
: DRBD/HA support and consulting             sales at linbit.com :
: LINBIT Information Technologies GmbH      Tel +43-1-8178292-0  :
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