LDN - Luminis Developer Network

 Very few people have clustered the resource tier.  I think this is the only posted success on Lumdev.

http://www.lumdev.net/node/617

You'd still have a single point of failure in your DB though, so you'd need to use an oracle solution, RAC maybe, to cluster the DB also.  Neither of which is supported (I think).

Parallel deployed web fronts is supported though, and fairly easy to set up.  

What we have done is somewhat extreme but still effective. We have a complete backup environment. Our Production system is a 13-webserver Parallel Deployment. We have a backup failover system which is a 9-webserver PD. The LDAP in the resource tiers for both these environents are in sync all the time (as essentially the same jobs, user imports are run on them simultaneously). Same with the two Luminis databases for these two environments. The only problem is with the corresponding Banner environments. Real time syncs can't happen on the backup Banner DB as it adds a lot of unnecessary overhead. The data on the backup banner db is always a day old. So far we haven't had to fall back to this backup environment thankfully.