[DRBD-user] DRBD: failover when sync connection dies?

Lars Ellenberg lars.ellenberg at linbit.com
Wed Dec 19 17:04:39 CET 2007

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

On Wed, Dec 19, 2007 at 04:05:04PM +0100, Martin Gombac wrote:
> >>How do you prevent the other node from trying to come and and  
> >>creating a
> >>split brain situation?
> >
> >use the drbd-outdate-peer handler and configure dopd.
> >yes, it has some issues as well, I know. we fixed some of those only
> >last week. as long as you don't use too many drbd, it should work
> >reliably enough with heartbeat 2.1.2.
> >make sure you configure a timeout (the default timeout is 60seconds,
> >which is longer than several other timeouts and causes cascading  
> >timeout
> >trouble), in short:
> >        outdate-peer "/usr/lib/heartbeat/drbd-peer-outdater -t 5";
> .... and have downtime for half of your services when you take  
> problematic node offline.

hey, you asked how to improve on avoiding split brain.
but also see the other mail.

> >>How do you get alerted that the sync is broken?
> >
> >nagios pages you?
> Nagios is cool, i use it, but probably won't help you with crossover  
> link. Altho there is nagios-nrpe which probably with custom plugins  
> would allow you to monitor it. In case you do write your own plugin  
> for this, forward it to me. ;-)

monitor the state of drbd.  anything looking like an ongoing
resync is a warning.  anything not "Connected", and not in the
above resync category is critical.

> >>How do you recover?
> >
> >fix the replication link.
> >reconnect drbd, if it does not do so by itself.
> Take the server offline and services that are on it with it. Fix it.  
> Bring it back. Be quick at it tho. Try to explain to the costumer why  
> the other node can't take over the resources even thou you sold them  
> fail-over clustered install.

see my other mail.

if your replication link is a spof, you have a spof.
eliminate it.

: 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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