[DRBD-user] 4-way redundancy problem

[Bart Coninckx]

On Wednesday 07 July 2010 18:23:53 Philippe Blondin wrote:
> Hi,
> 
> I'm trying to setup a 4-way redundancy using stacked DRBD resources.
> Unfortunately not much information is available, basically I'm trying to
> fallow the documentation for creating a three-node setup (except that
> the remote half of the DRBD configuration is also stacked, not just the
> local cluster) as written here :
> http://www.drbd.org/users-guide/s-pacemaker-stacked-resources.html
> 
> My setup is very similar to the fallowing figure except that all my
> nodes are on the same Cluster (same site).
> http://www.drbd.org/users-guide/drbd-resource-stacking-pacemaker-4nodes.png
> 
> Here's the interesting part of my DRBD.conf
> 
> ############################################
> 
> # Replication between Node1 <==> Node2
> resource mysql-left {
>   meta-disk internal;
>   device /dev/drbd0;
> 
>   on node1 {
>     disk      /dev/mapper/VolGroup00-data;
>     address   192.168.2.90:7789;
>   }
>   on node2 {
>     disk      /dev/mapper/VolGroup00-data;
>     address   192.168.2.91:7789;
>   }
> }
> 
> # Replication between Node3 <==> Node4
> resource mysql-right{
>   meta-disk internal;
>   device /dev/drbd0;
> 
>   on node3 {
>     disk      /dev/mapper/VolGroup00-data;
>     address   192.168.2.92:7789;
>   }
>   on node4 {
>     disk      /dev/mapper/VolGroup00-data;
>     address   192.168.2.93:7789;
>   }
> }
> 
> # Replication between stacked devices:
> #                       Left  <=====>    Right
> #         Stacked Node[1-2]               Stacked Node[3-4]
> resource mysql-stacked{
>   meta-disk internal;
>   device /dev/drbd10;    # Using another device for stacked DRBD
> 
>   stacked-on-top-of mysql-left {
>     address   10.0.0.10:7789;      # Using a Heartbeat IP, so it can run
> either on Node1 or Node2
>   }
>   stacked-on-top-of mysql-right {
>     address   10.0.0.20:7789;      # Using a Heartbeat IP, so it can run
> either on Node3 or Node4
>   }
> }
> 
> ############################################
> 
> Here's the step I've done so far:
> 
> 1. I've prepare both left and right side (lower level) by running
> respectively drbdadm create-md mysql-left on node1 and node2, and
> drbdadm create-md mysql-right on node3 and node4.
> 2. I've sync both sides.
> 3. I've setup pacemaker so my Heartbeat IP is running on node1
> (10.0.0.10) and node3 (10.0.0.20)
> Online: [ node3 node2 node4 node1 ]
> 
> res_ClusterIP_stacked_right     (ocf::heartbeat:IPaddr2):       Started
> node3
> res_ClusterIP_stacked_left      (ocf::heartbeat:IPaddr2):       Started
> node1
> 
> 3. Now I'm trying to prepare my stacked resource, so I put Node1 in
> primary mode (drbdadm primary mysql-left), but after when I want to
> initialize the internal data here's what happen ==>
> 
> [root at node1 etc]# drbdadm --stacked create-md mysql-stacked
> You want me to create a v08 style flexible-size internal meta data block.
> There appears to be a v08 flexible-size internal meta data block
> already in place on /dev/drbd0 at byte offset 11374563328
> Do you really want to overwrite the existing v08 meta-data?
> [need to type 'yes' to confirm]
> 
> It tries to overwrite my internal data for my /dev/drbd0 device.. I'm
>  pretty sure im missing something important here so I'm hoping someone can
>  enlighten me? It's the first time I'm trying to setup stacked resource,
>  please excuse my noobness ;P
> 
> Please don't hesitate to ask if you need any additionnal information, any
>  help is very appreciated!
> 
> Thanks
> 
> -Philippe Blondin
> 

I seem to have understood more than three is not supported. Or am I wrong?

B.