I currently have a 2x 1TB = 2TB RAID 0 from OWC. I use it on my MBP with a Sonnet Pro eSATA expresscard which delivers to me ~180/MBps peak speed, not bad. In the future I was thinking about upgrading the drives to 2x 2TB drives to make it 4TB. Or even better was thinking about getting a 8TB RAID 5 (4x 2TB). My problem is backing them up. The RAID 5 would at least have redundancy but I'm confused about backing them up. Since currently I have a 2TB RAID, I need to have a 2TB drive to back it up. If I wanted to make my RAID setup larger (i.e. 2x 2TB = 4TB RAID 0) then how would I be able to back that up on one drive (since there are no 4TB drives out). Would my only option be to buy another RAID 0 and set them up together as a RAID 0+1? In this effort, I have currently bought a dock with a WD Green 2TB drive. I thought I could start with this one and in the future I could buy the identical 2TB drive and upgrade my current setup..... In further down the line buy 2 more and consider changing the setup to RAID 5 (with a new OWC case). The time has come for me to purchase another 2TB drive and I just realized my first one was a WD Green drive. I'm not so worried about performance speed being slighting decreased by the Green drives since my bottleneck is topped at ~180MB/s with my expresscard. But does anyone know if the IntelliPower feature which "provides variable rotation rates in order to conserve power" could cause issues trying to set them up to work together in a RAID? I know WD makes 'real' RAID HDDs that happen to be expensive. I would not buy this anyhow since I'm on a budget. For those who object to this consider that OWC already ships their RAID setups with cheaper non-enterprise class HDDs. But if these Green drives would cause considerable other issues I would like to buy a different 2TB drive and start over accumulating them -- my first 2TB Green drive would be put to another use and I'll wait for next time to buy a matching drive for use in a RAID.