I can't speak to CentOS 6 but I have a few C5 HA clusters that use drbd for most cluster resources but use glusterfs for /home (and thus ~/public_html). Works fine. I can't check right now but I think I was using the native gluster client rather than NFS. Going by memory, I think the drbd main repo was supposed to be fine for use with centos as well. If you're replacing a system that worked well with drbd, I'd say stick with it. Glusterfs is fine, but drbd is less cantankerous and has fewer failure modes. I'm just waiting for CentOS 7 to come out and then those C5 clusters will get upgraded straight to C7. Devin (who hates typing with his thumbs on phone keyboards ...)