FileVault 2 was a great advancement for encryption on Mac OS X. It allowed for full disk encryption without the use of a third party product, as well as management using the system keychain or via a tool such as cauliflower vest.
One might ask “So how exactly do you upgrade a fully encrypted drive from 10.7 to 10.8?” As usual for all things FileVault related, Rich Trouton has you covered.
Although this may seem like a fairly complicated upgrade, it turns out that Apple has made it a fairly trivial task. Rich goes over the steps necessary to update your machine from 10.7 to 10.8 as well as a video to guide you through the process step-by-step. Check it out on Rich’s Blog.Source: Der Flounder