[DRBD-user] DRBD is passing I/O-error to upper layer, but should not

Lars Ellenberg lars.ellenberg at linbit.com
Mon Jan 28 18:26:50 CET 2013

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

On Mon, Jan 28, 2013 at 05:57:43PM +0100, Lars Ellenberg wrote:
> On Mon, Jan 28, 2013 at 04:04:32PM +0100, Matthias Hensler wrote:
> > Hi,
> > 
> > On Mon, Jan 28, 2013 at 03:26:49PM +0100, Felix Frank wrote:
> > > On 01/26/2013 06:19 PM, Matthias Hensler wrote:
> > > > Jan 26 15:32:21 lisa kernel: block drbd12: IO ERROR: neither local nor remote data, sector 0+0
> > > > Jan 26 15:32:21 lisa kernel: block drbd9: IO ERROR: neither local nor remote data, sector 0+0
> > > 
> > > I'm not at all sure about this, but this does seem to indicate that
> > > the peer either has disk problems of its own (not likely) or otherwise
> > > cannot access this specific (first?) sector.
> > 
> > I do not think that there were any disk problems on the peer. In fact I
> > did reboot all virtual machines on the peer side prior to replacing the
> > failed disk. Everything went smooth from there.
> Did you actually see DRBD pass errors up the stack
> (file systems remounting read-only, guest VMs noticing IO error),
> or have you "only" been scared by above log message.
> If the latter, we may need to do some "cosmetic surgery".
> If the former, and this node still had an established connection to a
> healthy peer device, we'd have a "real" bug.

Ok. I think we may in fact have a real bug there.
I still need to reproduce and double check, but it looks like
"empty flushes" (file system barriers) on a Diskless Primary
may be affected, obviously only on systems that do support those,
which is drbd 8.3.14 and 8.3.15, on kernels that implement "barrier"

drbd 8.4 should be good.

We'll see what we can do.

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

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