So I was thinking. I have an iMac (2012, for that matter) with a 1TB HDD. Which is slow, as all HDD's are I'm afraid. I also have an external HD of 1TB with a USB3 connection. My first thought was I'd combine them in a RAID-0 (striped) for performance. But than I thought: what if I'd make it a RAID-1. Than I'd be able to remove the HD in the future (for whatever reason, booting perhaps). I would not have the writing performance (hence the RAID-1) but I will be able to have reading performance of up to 250 MBps, right? Tell me guys, I have the feeling I'm missing something. What is it? EDIT: Just a second question. I have another 3TB drive. What if I combine my Macintosh HD (1TB, 60MBps read) plus my external HD (1TB, 60MBps read) plus a partition of my second external (1TB of 3TB, 140MBps read) in a mirrored RAID? Will that increase speed up to 260 MBps?