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

Dominik Klein dk at in-telegence.net
Thu Dec 13 14:42:44 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.


>> 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 the out of date resource on the other node comes up as primary.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 :-)

Your words are not clear. A crossover connection is usually considered a 
one on one connection between two computers. That's why I asked what 
would be different.

What you tell sounds more like you have two networks, an external and 
internal one.

To prevent your situation, you need to outdate your drbd peer or use 
Stonith.

Read:
http://blogs.linbit.com/florian/2007/10/01/an-underrated-cluster-admins-companion-dopd/
http://www.linux-ha.org/STONITH

Regards
Dominik



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