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

Martin Gombac martin at isg.si
Thu Dec 13 14:34:20 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 2007.12.13, at 14:08, Dominik Klein wrote:

>> i have a simple fail-over heartbeat/drbd cluster set up. In each  
>> server there are two network cards. One for internet access (WAN)  
>> and one for internal communication and synchronization (LAN). If  
>> one node looses internet connection (WAN) the other takes over all  
>> resources as expected, but this does no thappen with local  
>> connection (LAN) which is just crossover UTP cable.
>> In case if local connection (LAN) fails, cluster does not migrate  
>> all resources to one of the nodes and just continues to work  
>> without synchronized drbd resources (amongst other things).
>> My question is this:
>> How can i make one node take over all resources if local crossover  
>> connection fails?
> If the local crossover connection fails - what would be different  
> on the other node?
> I think its sane to leave everything as is.
> Or I understood your setup wrong or you explained it wrong :)

If the LAN/crossover fails, then:

- drbd doesn't sync anymore (so each node has one up to date resource  
and if i want to bring one down to replace network card which failed,  
the out of date resource on the other node comes up as primary. When  
i start node with replaced newtork card back, split brain would  
occur. Correct me if i'm wrong.)

- webmail and other apps stop working since they use internal network  
LAN/crossover for communication (faster, less busy). (I can go around  
this problem and just use external network (IPs) whenever  
communicating (mysql, smtp, imap,..) to other node, but it's less  
efficient and still doesn't fix above split brain problem.)

I hope i explained it :-)


> Regards
> Dominik
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