The original intention for parchive was to split files into multiples for posting on usenet. The bonus - you get n extra files, so that if any of the sub-files are broken, you can reconstruct it.

I use it for my backups, both automated and manual. For my photos, I write a set of 10-15 DVD-sized tar archives containing files that haven't been backed up yet, using a tool I wrote. I then run parchive to generate two or three DVD-sized ECC files, so if any one DVD gets trashed I can recover it. Then it's just a matter of burning the DVDs and stacking them somewhere off-site.

That's very fiddly compared to using ZFS and getting it "for free".

Depends on what you find fiddly. With par2 I can move the files to other filesystems without problems, not being bound to ZFS (bsd) means a lot to me. I will reconsider when Btrfs is stable.

Unless ZFS isn't easily available on the OS you are using.

Linux has an easy to install port (http://zfsonlinux.org/). I remember OSX as having to use it via FUSE. I guess that leaves only Windows.

OS/2 had installable filesystems. Does Windows have something like it?

OS X has a native port - http://open-zfs.org/wiki/Distributions#ZFS-OSX

Windows has ReFS - http://en.wikipedia.org/wiki/ReFS

I didn't mean like ZFS, but like installable filesystems. It should be possible, with some effort, make ZFS run on Windows.

ReFS is beta-quality and lack several features ZFS has since its first production-grade release. It's not really an apples to apples comparison.

And if you don't want to do it manually, use solutions that already do this along with other nice stuff: I'm thinking about Snapraid[0] for instance.

[0] http://snapraid.sourceforge.net/compare.html