[DRBD-user] Adding additional 'node' to DRBD

[Roland Kammerer]

On Wed, Jan 16, 2019 at 09:47:05AM -0500, Shawn Southern wrote:
> I'm very new to DRBD, so please bear with me if my terminology is wrong (or
> if I've completely done everything wrong, please let me know!).  I've not
> had much luck with finding this scenario in the documentation.
> 
> Initially, I only had a single system I could configure.  The other
> identical system was running Hyper-V, so I had to get a system up with
> CentOS, KVM & DRBD then migrate the workloads, then reformat the Hyper-V
> box as CentOS, KVM & DRBD).
> 
> System 1 (vmh1) is 10.13.119.15, System 2 (vmh2) that I have to add is
> 10.13.119.16.  I've got the workload migrated to 'vmh1' and 'vmh2' is now
> reinstalled with CentOS, KVM & DRBD.  What I need to know is how do I
> safely add the sdb & sdc in vmh2 to the existing single node DRBD so that
> it safely replicates the data and I don't lose my workload?

On both sides you change the res file like this:

> 
> in /etc/drdb.d I have:
> file global_common.conf:
> global {
>  usage-count no;
> }
> common {
>  net {
>   protocol C;
>  }
> }
> 
> file drbd0.res:
> resource drbd0 {
>         device /dev/drbd0;
>         meta-disk internal;
>         net {
>                 cram-hmac-alg sha256;
>                 shared-secret "ThisIsSecret1";
>         }
>         on vmh1 {
>                 node-id 1;
>                 address 10.13.119.15:7789;
>                 disk /dev/sdb;
>         }

^^ you add a "on vmh2" section with a different node-id;

^^ you add a "connection-mesh" section naming both nodes.

> }

Then you:
- "drbdadm create-md" meta data on the second host
- "drbdadm adjust" on both.

Regards, rck