Let's look at this conundrum, which is flawless management of files across computers. The confusion over where data gets stored and fetched from can be resolved owing to remote login. Assuming we speak of high-bandwidth networks here (100Mbit LAN in my case), the 'cost' of using SSH bandwidth is almost negligible. Even 10Mbit connections would give you a very responsive UI behaviour over the network. I know this because I tried it. The exception are cases where you stream many large frames over the network (e.g. video, games).

I have never looked deep into RAID technologies. Why not just scp (or rsync) the entire content of a hard-drive periodically. I maintain files on just a single machine, which I always SSH to from elsewhere. Its contents get mirrored on two other remote machines. Files that change on a daily basis are backed on the SAN overnight using cron jobs. This simplifies life a great deal. I still see no compelling reason for using RAID, especially with the existence high-speed networks.