I’ve been mulling over building a FreeNas box for awhile, mostly so I can work remotely and share files with clients without one of those goofy file-share sites. I decided it was time to learn about mirroring/parity – these two pages were incredibly helpful:
http://riceball.com/d/content/raid-5-parity-what-it-and-how-does-it-work
http://www.prepressure.com/library/technology/raid