I installed Yosemite on an disk formatted as Mac OS Extended (Journaled, Encrypted). For this purpose I entered a password. When I booted the machine up I got three icons on the logins screen: My User. Encrypted Drive. Guest User. Once I had logged in FileVault was active in the System settings. After a bit of research I found out that to get rid of the Encrypted Drive login icon I had to deactivate FileVault and then reactivate it, so I did that. It took forever but now there is no Encrypted Drive icon on the login screen. The thing is that when I reactivated FileVault I was given a Key as opposed to entering a password. So I'm left wondering what is the difference between installing OS X to an encrypted filesystem and installing OS X to a garden variety unencrypted Mac OS Extended volume and activating FileVault afterwards? I always figured these two methods basically end up giving you the same result. Plus, why did I have to enter a password when I created the encrypted volume the first time but got a key the second time when I re-activated FileVault? Am I now double encrypting my disk?