I've been pondering for a long time about how I can set up a server which operates much like the Drobo storage thing. The reasons I don't actually want a drobo is because I've heard scare stories, plus I'd like to do this on the cheap.

So ideally I'm looking for something like lvm so I can create a logical volume that spans many hard disks of varying sizes... obviously that only offers redundancy if I put the LV on a raid array (as far as I know..) I have however been reading about technologies such as Microsoft's drive extender which duplicates files at the filesystem level and makes sure that the mirrored files are on a different phyiscal disk.. does anyone know or recommend a filesystem or method like this as it'll hopefully make much better use of the space available than raid ever could.

Performance isn't an issue, I'd just really like to make the most of the hard disks I have lying around whilst having a bit of redundancy incase a disk dies. I understand full well that this is no replacement for a backup, but I'll only be storing files of medium importance and using the nas itself as a backup of my main pc and other systems.

Thanks in advance! I'm hoping zfs or btrfs or something can do something clever for me :)