OK, these might be some obvious questions, but I could use some advice on drive configuration. Here's my mac pro setup, all internal drives: 1. 250GB - System and Apps, work files 2. 500GB - Time Machine target drive (backs up everything from 250GB) I ordered a new 750GB from Newegg. Actually, I ordered two accidentally. I could return the extra, but wondering if I should keep it and outfit my machine as follows. 1. 250GB - System and Apps 2. Partition the 500GB into: PARTITION A, 250GB : RAID 1 Mirror of Drive 1 (System and Apps) -- So I have a bootable exact duplicate of System drive and all Apps, that is constantly updated. *** PARTITION B, 250GB: Photoshop Scratch, old archive, or maybe a Windows boot 3. 750GB - All of my documents, and photography work files 4. 750GB - Time Machine target drive (backs up everything from drive 3). Using Time Machine instead of a mirrored RAID 1 here so that I have the flexibility of going back to older versions if need be.... at least when drive isn't to capacity. *** Questions: 1. Can you run a RAID 1 using a partition. That is, can I create a RAID 1 between Drive 1 and Partition A of drive 2. 2. Do both drives need to be blank when I set up a RAID? All my System and Apps are on drive one -- will I be able to set up the RAID 1 with Partition A without having to erase it and reinstall everything? I appreciate the guidance.