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

Trey Dockendorf treydock at gmail.com
Thu Dec 15 18:55:42 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 Dec 15, 2011 10:22 AM, "Felix Frank" <ff at mpexnet.de> wrote:
> Hi,
> 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
> leisure.
> Cheers,
> Felix

All the qcow images are in pools located on the same logical volume.

Your correct.  The plan is to migrate before the fiber repair and network
outage then sync them back with DRBD.

The meta space, does it have to be stored separate from the replicated
LVM?  I have a few 100 GBs left on that device.

- Trey
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