[DRBD-user] Default Split Brain Behaviour

Lew ls at redgrid.net
Mon Jan 24 01:20:01 CET 2011

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

I've encountered some unexpected behavior with a split brain instance. 
It seems from what has occurred that the default behavior is set to roll back & discard changes. 

Recently in my sand pit, I've been manually disconnecting resources as a an ad hock way of maintaining a snapshot for roll back. 
This way if I'm happy with changes, I can reconnect and within seconds we're fully synced again. 

I moved a server yesterday and discovered after a drbdadm connect all, that one of the resources had split brained and discarded a few days worth of work; 
rolling back to the point in time when the resource was first disconnected. 

What's interesting to me is that the disconnected secondary node had never been set primary, so how did we end up in split brain? 
I also do not understand why it was only this resource that split brained, when others that existed in seemingly identical configurations and states did not. 

I expect I'll need to explicitly prohibit this behavior in a global net section covering after-sb-0pri etc; 
I still don't understand why discard & roll back has been chosen default behavior, I'm contending from my experience it should not be. 

Looks to me like a few days work is lost, but if anyone knows of a way to recover from a roll back discard scenario, I'd be very happy to find out. 


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