[CentOS] Recommendations

We have two virtual machines on ESX 3 running CentOS 4.3 and we'd like
to turn them into some sort of highly available nfs file server.
Currently, I am familiar with DRBD and RHCS but I was curious what
others might recommend in such a situation.

I'm not sure how easily we could use RHCS in such a situation because we
don't really have the advantage of shared storage in this setup.  We are
strictly limited to the two boxes.  Having said that, it would be nice
to have some of the exports running on one node (tied to a VIP) and
others on the other node (tied to another VIP) if possible and manage
those services individually if needed.  So basically both nodes would be
exporting select locations at any given time on this highly available
file system.  That is not 100% necessary but it would be nice if the
capability is there.  I would assume some sort of fencing mechanism
would need to been in place as well.

This might not be the best place to ask an ESX question but would 'raw
device mapping' work in such a scenario?  I don't know much about it.

I can give more details if needed but hopefully this is enough for some
suggestions.  Thanks!