Best way to build home NAS with redundancy [closed]

Freenas is great. I would look at the rsync options in freenas to get the redundancy you want/need if you don't want to spend the money for the sata card

FreeNAS or OpenFiler or even just straight Debian or Ubuntu distro (for ease of package install/deinstall) would be my choices.

For backups, though, I'd also consider getting things offsite via something like Mozy or AllMyData.com.

I am personally working on setting up an at home NAS using OpenSolaris and ZFS. ZFS will support redundancy, pairing multiple drives of different sizes into a single virtual volume (or pool).

In addition, ZFS supports a great feature called "snapshots" which allows you to take instant, lightweight shots of the system for later recall. Integrity checking is performed constantly so that your data is always kept safe (or at least you know when it's not).

Of course, ZFS is still very much in testing.

For what it's worth, I've been using an HP MediaVault with good success. Two drives mirrored.

I backup my most sensitive and critical files (financial, personal records) to matched set of thumb drives that stay in a fireproof safe. Other stuff (pictures, home videos) go to DVDs. These can easily be stored off-site.