[DRBD-user] drbd split brain recovery - workaround?

Lars Ellenberg Lars.Ellenberg at linbit.com
Thu Sep 29 15:06:09 CEST 2005

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


/ 2005-09-30 00:58:34 +1200
\ Jonathan Wheeler:
> #!/bin/bash
> drbdadm=/sbin/drbdadm
> 
> if grep -q Unknown /proc/drbd
             StandAlone would probably be more what you mean.
> then echo "we have a broken drbd connection"
> $drbdadm connect r0
> fi
> 
> exit
> 
> 
> 
> This was then added to cron on both machines, and set to run every 10
> minutes, offset by 5 per server. This allows the system to work with
> either host running as the active node
> 
> 
> For me... this has fixed my split brain problem. This still isn't
> sophisticated enough to allow for a HA auto-fallback, but at least I
> have data synced on both disks increasing my redundancy until a) I
> switch back manually, or b) another failure takes out the failed over
> node, in which case this will have saved my bacon.
> 
> Now, I might be misunderstanding exactly what drbd connect does. At face
> value this appears to simply be initiating a connection with it's peer,
> and it seems to me that this is something that drbd should be able to
> take care of itself internally.
> I have my connect-int set to 10 seconds, but from what I'm seeing here,
> they try *ONCE* and give up. A simple retry (in the "other" direction)
> should allow for a successful resync?

they only give up if the situation won't change, i.e. if they know it
would be pointless, or worse, might risk your data.
if they recognize that you (might) have different versions of data on
the nodes, they try to avoid the automatic resync, because you might
chose an other direction than what might result from the automatic rules.

> As an intermediate step before 0.8, is this something that could be
> implemented in 0.7x?

no.

-- 
: Lars Ellenberg                                  Tel +43-1-8178292-0  :
: LINBIT Information Technologies GmbH            Fax +43-1-8178292-82 :
: Schoenbrunner Str. 244, A-1120 Vienna/Europe   http://www.linbit.com :
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