[DRBD-user] RHCS and dual primary

[splitbrain]

Digimer wrote:
> 
> On 04/08/2011 11:22 AM, Cristian Mammoli - Apra Sistemi wrote:
>> Hi, as far as I understand from the docs, DRBD as a RHCS resource is
>> only supported as single primary.
>> If I need to use it as a dual primary device for GFS or CLVM I need to
>> start it BEFORE cman and manage it outside of the cluster.
>> Right?
> 
> Nope. :)
> 
> I use DRBD Primary/Primary extensively in RHCS. What I do is add it as a
> script resource along with clvmd and gfs2. Then I create two failover
> domains, one for each node, that is restricted and contains only that
> node. Then for each failover domain, I create a service tree that
> starts, in order, drbd -> clvmd -> gfs2.
> 
> Then you can create normal services, failover groups and whatnot.
> 
> -- 
> Digimer
> E-Mail: digimer at alteeve.com
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> 

I was able to do this as well except I also used a virtual IP. I tried to
get the drdb.sh and drbd.metadata stuff working with RHCS but I didn't have
any luck. I ended up just using the /etc/init.d/drbd script and it appears
to work fine.

So I used a nested service with the following resources Virtual IP -> DRBD
-> CLVM -> GFS2 -> nfs export.

My DRBD resource as defined in system-config-cluster is just a script which
points to /etc/init.d/drbd.

I tested relocating the resource via "clusvcadm -r <service> -m <node> and
it worked. I tested powering off the working node and the service migrated
to the other node, and I tested just running "/etc/init.d/drbd stop" on the
working node and the service relocated.

The tricky thing was the drbd.conf. I didn't use the "on host" keyword. I
used "floating" and listed both virtual IPs:port. Also, you have to list the
floating IP:port last. If you put meta-data after them, drbd startup
bitches.

My drbd.conf looks like this:

resource r0 {
   startup {
      become-primary-on both;
   }
   protocol C;
  
               device        /dev/drbd1;
               disk           /dev/dm-1;
               metadisk    internal;
               floating       <insert virtual IP:port here>;
               floating        <insert other virtual IP:port here>;
     net {
           allow-two-primaries;
           after-sb-0pri discard-zero-changes;
           after-sb-1pri  discard-secondary;
           after-sb-2pri call-pri-lost-after-sb;
    }
}
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