Currently, I have a rather basic 13TB setup comprised of a few different sized drives mounted on various /media/ mount points but I'd like to shift that to a single big "drive". This sort of stuff is going over my head so I was wondering if you guys could give me some advice? I've heard ZFS mentioned a few times. I really don't want to need to buy anything new, hardware-wise, though. Could stretch to a paid-software solution though.

I'd like it to have some resilience to failing/corrupting, although my most major concern there would be if one HDD dies, would all the data be lost? Maybe some parity thing? Also support for multiple sized HDDs, adding and removing them is pretty vital. That incremental backup/shadowing thing that's been mentioned looks good too.

Any advice you guys can give?