Sorin Srbu wrote:

Today I have five 500GB-disks raided on linux machine. Remove one for parity and I have 2TB of real space available. Doing a 0+1, ie 1TB, would indeed be better as performance goes, but 1TB of space, well, it just isn't enough unfortunately.

As it is now, the 2TB shebang is mounted as /backup. Does that count as a single filesystem?

I was thinking about your long term here. Make sure to use LVM to create your underlaying partition. Then you can add disk space in the future without having to reformat everything and can just grow your ext3/ext4 partition instead.