We have been testing GFS with ext4.
I'm not sure how that was configured since that was done by our internal helpdesk. I'm currently gathering information on how to configure GFS to place it on the manual and a blog.
You should be able to find how to configure GFS on RedHat docs, or you should find the same if you use any other SAN provider.
The only requirement we have is distributed file locks should work if you chose another solution different GFS.
Thank you for the quick reply!