[DRBD-user] ocf:linbit:drbd: DRBD Split-Brain not detected in non standard setup

Lars Ellenberg lars.ellenberg at linbit.com
Fri Feb 24 15:53:51 CET 2017

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

On Fri, Feb 24, 2017 at 03:08:04PM +0100, Dr. Volker Jaenisch wrote:
> Hi DRBD_users!
> We have a drbd 8.4 setup with two nodes over distance lines, with one
> not so common feature, we like to discuss here.
> Host A ========== 2 x 10GBit lines ========  Host B
>    | --------------- DSL 2Mb/s Line ------------|
> The nodes are connected via two redundant 10Gbit links which are port
> channeled/bonded in an interface bond0 on the nodes. Lets call this bond
> the "worker" connection.
> Pacemaker (corosync) features two rings: One over bond0 (the worker
> connection) and the second over an additional link (DSL peer-2-peer
> 2Mbit/sec). Lets call this DSL-Link the "heartbeat" connection. This
> additional hearbeat line is the non standard part.
> The configurations of corosync, pacemaker, drbd are from the textbook
> and in no way spezial.
> Testing disaster szenarios we discovered the following corner case:
> If both 10Gbit links fail then the bond0 aka the worker connection fails
> and DRBD goes - as expected - into split brain. But that is not the problem.

DRBD will be *disconnected*, yes.
But no reason for it to be "split brain"ed yet.
and with proper fencing configured, it won't.

> The problem is that pacemaker obviously does not notice the split brain.

No split brain yet.
So why would it notice.

> So pacemaker cannot solve this condition by itself. But

Yes it can.
Or you did not provide enough context.

: Lars Ellenberg
: LINBIT | Keeping the Digital World Running
: DRBD -- Heartbeat -- Corosync -- Pacemaker

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