You Need to See What These Folks Have to Say
I must put out a plug for Oracle’s Maximum Availability Architecture (MAA) team and the fruits of their labor now that I have personally worked with them on projects for over a year…I’m sure it’s no credit to them that I should say so, but honestly, this team is really, really sharp!
Not only is this paper covering migration to Exadata Storage Server helpful for the actual act of deploying Exadata into an existing Oracle DW/BI environment, but it also goes a long way to suggest how much simpler it surely must be than dumping out an Oracle database and loading it.
Go get some of those papers!
Kevin Closson's Blog: Platforms, Databases and Storage 
… this team is really, really sharp!
Strange timing. I was just recommending their work to a colleague today who has to get up to speed on HA stuff very quickly.