According to Oracle pre-sales around 95% of Oracle RAC customers are using ASM (Automatic Storage Manager). So if you are studying another Cluster filesystem solution stop it, moreover the product is free as coming in 11gR2 Grid infrastructure installation included in huge RAC license fee.
On top of ASM Oracle is now proposing a cluster filesystem called ACFS (ASM Cluster File System). Initially the product was free and it was possible to use it to store your applicative files (non-Oracle files). There are lots of blog posts on this subject over Internet and it’s difficult to know who is right or wrong.