[DRBD-user] Install DRBD on a running system to replicate it

Daniel Meszaros spam at meszi.de
Thu Aug 11 10:25:11 CEST 2011

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

Am 10.08.2011 22:10, schrieb valbzh:
> Hello,
> I would like to know first if it is possible to install DRBD on a running
> system (NFS server in my case) in order to link it to an other empty server
> and sync them.
> I don't want (can't) shutdown this server and I need to migrate it to a
> replicated solution without turning it off.
> Thanks. Val
Hmm, IMHO the necessary steps would be:

1. Find an almost identical machine (hardware).
2. Install the system and DRBD onto the new machine. Single primary.
3. Set up the DRBD device, create FS and mount it.
4. Rsync the data from the old machine to the DRBD device of the new 
machine and verify if data was synced without errors.
5. Set up and start NFS on the DRBD device of the new machine and pass 
the NFS server function to it. Disable the NFS export on the old one.
6. Set up DRBD on the old machine. Secondary.
7. Sync both DRBD nodes.

No need to delete the old NFS export's data unless you don't need the 
disk space. You can still delete it when you are 100% sure that the new 
setup works fine.

If both machines shall be able mounting the DRBD devices you need to use 
a dual-primary-capable FS like GFS2. Both machines would export the same 
data - probably nice for failover things. Otherwise you can still have 
the secondary machine switch to primary mode, mount the DRBD device and 
start NFS in a failover situation (i.e. the former primary drops the 

I myself am just setting up a dual-primary KVM solution here.


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