[DRBD-user] "BAD! BarrierAck"... after split brain.

Lars Ellenberg lars.ellenberg at linbit.com
Mon Sep 9 10:42:09 CEST 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 Tue, Aug 13, 2013 at 09:46:25AM -0430, Jose Ildefonso Camargo Tolosa wrote:
> Hi!
> 
> To answer myself on this, I commented-out these settings from
> configuration, and this started to work again:
> 
> disk-barrier no;
> disk-flushes no;
> disk-drain no;

man drbd.conf, disk-drain

  ...

  none

  The fourth method is to not express write-after-write dependencies
  to the backing store at all, by also specifying no-disk-drain.

  This is dangerous on most IO stacks, may result in write-reordering,
  and if so, can theoretically be the reason for data corruption,
  or disturb the DRBD protocol, causing spurious
  disconnect/reconnect cycles.
  
  Do not use no-disk-drain.

> Still, I would like to know your opinion on this, why would this settings
> cause such a message? and, why only after a failure?
> 
> Thanks!
> 
> Ildefonso.
> 
> On Mon, Aug 12, 2013 at 5:39 PM, Jose Ildefonso Camargo Tolosa <
> ildefonso.camargo at gmail.com> wrote:
> 
> > Hi!
> >
> > I had a server issue recently that produced an split brain (no big deal
> > this far), however, when I tried to resync, I started to see this messages
> > in new master server:
> >
> > d-con shared: BAD! BarrierAck #547846 received, expected #547845!
> >
> > Where the first number is always greater than the second by 1.
> >
> > This is Kernel 3.10.5, in-kernel DRBD 8.4.3.
> >
> > Any ideas?


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

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