Software raid via mdadm is a good option. Setup a raid 1 or 1+0 md device for your two disks. E.g. /dev/md1 = raid1 of /dev/sda1 + /dev/sdb1. Now format and use the /dev/md1 partition as full disk encryption, or a truecrypt container with ext4 inside, whatever you like. Now when one disk dies, mdadm emails you, and you can still read/write to the array (where only one disk is active).
I tend to partition and max out the available space on every drive, so LVM is an unnecessary layer for me.
You still need backup for file corruption, accidental deletion, or when both drives fail at the same time.