Since I've had dual hard drives OS X onward (Beige G3 required partitioning the HD). I've always had a OS/Apps drive as well as a separate Data Drive. With the Retinal MBP being my first ever portable, I partitioned it 70/180. I am now wondering if I should just stick with a single drive and use FileVault2 for security. The reason I love having seperatge OS/Apps and Data partitions/drives is so that I don't have to care about my boot drive. With every OS upgrade, I always clean install. and sometimes throughout the year clean install. I've been using Time Machine via my Drobo FS on my Mac Pro (4 drives) for 2 years). But doing a restore at install time I don't know why but I don't trust it. So what are your thoughts? I average around 2-4 clean installs a year to clean out the build up of junk on the boot drive.