you don't need RAC

a very good white paper http://www.my-idconcept.de/downloads/You_Probably_Dont_Need_RAC.pdf

One way of looking at availability is this: If you have a standalone Unix box it will
usually give you 99.9% availability over a year (some say 99.5, some say 99.9). It just runs. And so does Oracle usually. If you have a two-node Unix cluster the availability over a year drops to 98%.

If you need to cover your behind politically in your organisation, you can choose to buy clusters, Oracle, RAC and what have you, and then you can safely say: “We’ve bought the most expensive equipment known to man. It cannot possibly be our fault if something goes wrong or the system goes down”.
Otherwise, you probably don’t need RAC. Alternatives will usually be cheaper , easier to manage and quite sufficient.