[Linux-HA] Distributed file system with DRBD configuration?

[Hunny Bunny]

Hello cluster folkz,
I managed to install and configure DRBD on 3 node cluster. Node1 is a primary, node2 is a secondary and node3 is a stacked-on-top-of "node1_node2" backup.

Now I would like to use distributed FS either OCFS2 or GFS2 for the direct concurrent access of MySQL, SVN and other shared data from all three nodes.

If I enable allow-two-primaries for the node1 and node2 can I still use node3 as a stacked-on-top-of "node1_node2" backup, or it is off the table in allow-two-primaries configuration schema?
 
I could not find any DRBD configuration example which would allow to use three nodes simultaneously something like "allow-three-primaries" without "stacking on top of" thing.

Could  somebody please enlighten me on this issue.

Many thanks in advance,

Alex