[DRBD-user] DRBD failover between datacenters if one's network fails

Felix Frank ff at mpexnet.de
Thu Dec 15 17:22:57 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.


On 12/15/2011 05:09 PM, Trey Dockendorf wrote:
> Thanks for the input.  Your right in that 2 days is too little time to
> do this, so I'm going to manual route of shutting one server down at a
> time, migrating the virtual disks then bringing it back up on the remote
> site.

I had thought the QCow images were on one disk. If there are indeed
several disks you can sync, yes, you can take that route.

> To avoid more downtime of manual migration once this is all over with, I
> think I will first attempt just getting a DRBD resource up and running
> to sync my servers back to the primary datacenter.  Can a DRBD resource
> on an existing LVM be done without effecting the data ?  Also since I

Yes, provided you can a) enlarge the LV a bit to use internal meta data
or b) have some extra space on both machines to create an external meta
data disk.

> don't plain to have automatic failover, any precautions I should take if
> the network connection is lost between the two datacenters ?  Ideally
> this would allow me to have minimal downtime while the nodes re-sync.

Resyncing does not require downtime. Migrating the VMs to the other DRBD
peer needs downtime, and it's always brief.

I cannot think of any required precautions.

So the actual plan is to migrate the VMs before the connection is lost?
Great, this way you get away with an (arbitrarily long) quicksync once
the link returns and once that's finished, you can migrate back at your


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