For rac, you are going to need several separate shared disks between the two servers.
You need at least 1 OCR and 1 Voting disk.... no bigger than 100M each. Best practice is to have 2 OCR and 3 Voting, but this is a test environment so that is a bit of overkill. Then you will at least need 1 shared disk for data. My suggestion is to use ASM over ocfs. ASM is far better and most big RAC environments that I have worked on use it.
As much as I love Gentoo, RedHat seems to work best with Oracle. You might want to look at CentOs as the OS to run.
There are pretty comprehensive guides to running Oracle on RedHat here
ORACLE-BASE - Linux and Oracle
That might help you get started.