Oracle released a paper on how to build your own Oracle RAC Cluster on Oracle Enterprise Linux and ISCSI. The guide will help you to build your own RAC cluster for under US$2600. I however states that this is only for a testing environment and not for a production environment. The paper will go over most basic points of your hardware environment and storage solutions.
On the storage part there are some notes that go “against” the use of a standard NAS/NFS and tend to go more for a Direct NFS Client approach, Direct NFS Clients will integrate NFS directly to Oracle and by doing this Oracle will be able to control and fine-tune the I/O path between the Oracle software and the NFS server resulting in significant performance gains. In the example however will be worked with a ISCSI solution.
For the rest it will guide you step by step installing all the nodes and setting up networking and other environment parts. A great guide when you like to start with RAC in a test environment.