Clustering and vpopmail questions

[tamer]

Hi   Sorry if I am little off vpopmail topic. I was wandering if someone has ran vpopmail+qmail in a clustered environment. I am thinking maybe RAID + Fiber Channel. Thinking/reading about QMTP, NFS (definitely maildir, and the broken nfs file locking feature?). Maybe AFS, Coda, GFS? What about Qmail-LDAP? Would vpopmail handle a 6 million user domain spanned across a 40 server cluster maybe? Ideas would be appreciated.   Tim