I've been reading through some articles on hard drive performance and I have come across several interesting ones that claim that I should leave empty half of the hard drive (or partition?) that my OS resides on in order to maintain optimal performance and speed. One reason given is that it keeps data on the outer parts/layers of the hard drive, which are supposedly accessible much faster than the inner parts of the drive. As a hard drive fills up, data is written to the inner (and slower) part of a hard drive, including applications that I might install at a later date as well as common OS files. This setup is supposed to make for a better and faster user experience on a day-to-day basis. I must say that I think I have recently experienced that myself, as I filled up 900GB of my last iMac's 1TB drive and even boot-up was painfully slow. My current setup is 900GB free, and only 100 gigs in use. Should I partition the drive to where the system (OS) partition would be allocated, let's say, 300GB, and I would leave at least 150GB free for the aforementioned reasons? I wouldn't want to leave half of my 1TB drive empty, as that sounds like a waste of space. I'd be very appreciative for any advice, recommendations, things I should and should not do, etc. Boy, do I miss my Intel SSD, where this is no longer an issue.