Many enterprises' high-availability architecture is based on the assumption that you can prevent failure from happening by putting all your critical data in a centralized database, back it up with expensive storage, and replicate it somehow between the sites. As I argued in one of my previous posts (Why Existing Databases (RAC) are So Breakable!) many of those assumptions are broken at their core, as storage is doomed to failure just like any other device, expensive hardware doesn’t make things any better and database replication is often not enough.