[DRBD-user] DRBD metadata issue + replacing a disk

Lars Ellenberg lars.ellenberg at linbit.com
Thu Oct 15 15:34:51 CEST 2015

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


On Thu, Oct 15, 2015 at 03:02:18PM +0300, Ammar Sheikh Saleh wrote:
> > "JBD: Spotted dirty metadata buffer" turns up several bugzillas from
> > 2010 and 2012, suggesting kernel upgrade would help.
>
> When ==>  During normal operation
> 
> What's the IO stack below DRBD  ==>  4 Disks in JBOD
> 
> Kernel upgrade is not possible now  ... but at the same time its not too
> old  ( v.2.6.32-431.20.3)

What the message is complaining about is that JBD (the journaling
component of ext*) detects a buffer that is "dirty" (under write-out),
when it did not expect it to be.

This all happens before any IO request related to that buffer even
reaches the block layer or DRBD.

Maybe you have some "live dump" going on or do some other "unexpected"
(by JBD) things. Or your kernel simply still has some bug/race in the
related IO paths.

In any case, this has nothing to do with DRBD, as the error message
complains about something happening in the buffer/page cache,
which is *above* DRBD.

So whatever happens there, would happen just the same, even without DRBD.
(Though, of course, DRBD changes timings and memory pressure, so it may
make it more or less likely to trigger this).

> > On Thu, Oct 15, 2015 at 12:32:11PM +0300, Ammar Sheikh Saleh wrote:
> > > Hi all,
> > >
> > > I have one cluster with 2 nodes in active-active - master/slave setup
> > >
> > > I see the following error messages in the system logs:
> >
> > *when*.
> >
> > After a hard crash?
> > After a simulated Crash?
> > After a switchover?
> > After a failover?
> > During normal operation?
> >
> > What's the IO stack below DRBD?
> >
> > > Jan  5 22:02:18 lws1h1 kernel: EXT4-fs error (device drbd1): ext4_mb_generate_buddy: EXT4-fs: group 3795: 32532 blocks in bitmap, 29780 in gd
> > > Jan  5 22:02:19 lws1h1 kernel: JBD: Spotted dirty metadata buffer (dev = drbd1, blocknr = 0). There's a risk of filesystem corruption in case of system crash.
> > >
> > > What is the appropriate action to fix this issue
> >
> > Did you even google for the message?
> > "JBD: Spotted dirty metadata buffer" turns up several bugzillas from
> > 2010 and 2012, suggesting kernel upgrade would help.


-- 
: Lars Ellenberg
: http://www.LINBIT.com | Your Way to High Availability
: DRBD, Linux-HA  and  Pacemaker support and consulting

DRBD® and LINBIT® are registered trademarks of LINBIT, Austria.
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