[DRBD-user] Handling failback

Federico Fanton fake at panizzolo.it
Wed Oct 15 10:44:17 CEST 2008

Note: "permalinks" may not be as permanent as we would like,
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Hi everyone!
I'm setting up a little cluster with two identical machines running 
CentOS 5.2 and drbd 8.2.6.
drbd is mirroring a logical volume that contains a Xen 3.2.1 domU, which 
is running a Samba server. The domU's configuration uses drbd directly 
(disk=[drbd:samba-disk,xvda1,w]), so Xen handles drbd state.

Right now I'm testing failover/failback *without heartbeat* (for 
simplicity of testing) and I can't figure how a way to handle failback :(

My test goes like the following:
Initially drbd is in Connected Secondary/Secondary mode

-> Start the VM on node1
drbd on node1: Connected Primary/Secondary

-> Unplug network cables from node1 to simulate a failure
drbd on node2: WFConnection Secondary/Unknown

-> Start the VM on node2 to simulate failover
drbd on node2: WFConnection Primary/Unknown

-> Copy a file via Samba

-> Reconnect node1
drbd on node1: WFConnection Primary/Unknown
drbd on node2: StandAlone Primary/Unknown

What should I do now to reconnect drbd so that I don't lose the file I 
copied via Samba?
I think I should stop the VM on node2, reconnect drbd (which I don't 
know how) and restart the VM on node1, am I right?

Many thanks for your time!
(Sorry if this isn't the right ML for my question: as there are so many 
interconnected technologies in play, it's a bit tricky to figure out 
each one's responsibility ^^; )




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