I've seen it here before where people say performance goes down significantly as your HDD fills up. Some explanations have been about the platters having lower read speeds as data writes towards the inside, but I've seen such claims rebutted. My new MBP is maxed out with RAM and I have multiple external drives. My internal is 500Gb and I've always worried about keeping it under 75% full, but if it's not necessary I would like to add my photos and music to it. Can someone please shed light on whether or not it effects HDD performance? (I'm not talking about when you have under 5Gb or even less available) Also, since I do heavy graphic and video work, is it important to have a scratch disk not on my media drive? My media drive is currently a RAID 0 I have hooked up via eSATA. I thought dedicated scratch drives are a thing of the past. Should I use my external FW800 (non-RAID)?