I have a CentOS 6.3 client that needs to access NFS storage. There are two NFS servers that serve up the same content stored on a SAN with a clustered filesystem. How do I set up CentOS to failover to the backup NFS server if needed? When I Google, I keep reading that Linux does not support this, but that would be strange since there is plenty of information out there on how to set up a clustered Linux NFS server farm...
That sounds like a job for the automount(8) daemon. See the autofs(5) man page (from the autofs rpm) under "Replicated Server". I believe if you add a line like
to /etc/auto.misc on your client and (re-)start the autofs service, your NFS storage will show up under /misc/fileserv. You could add -ro as mount options if you want to mount read only (or other mount options of course).
The Right Way(tm) to do this is with GlusterFS, which is a scale out filesystem that runs in userspace atop an underlying filesystem like NFS or CIFS.
All this sounds impressive and complicated, but it's actually really simple to set up. It honestly should take you less than 15 minutes. You'd have two servers, each with a "brick" (unit of storage) defined. A volume would then be defined within this server pool. Replication of the data between the servers happens automatically, as does failover on the client if one of the servers dies.