I have an encrypted 5TB setup using LVM, dm-crypt, and XFS in two identical full-size ATX 8-bay chassis, with nightly rsyncs from the primary to the secondary (

I have an encrypted 5TB setup using LVM, dm-crypt, and XFS in two identical full-size ATX 8-bay chassis, with nightly rsyncs from the primary to the secondary (with a simple versioning script that I wrote). Every year, I buy the biggest hard drive I can for $100 and replace the oldest drive in each system. LVM makes it extremely easy to move all of the blocks off of a drive and remove it. I also run smartd on both systems and replace a drive at the first sign of a serious error. I used to run RAID hardware cards but changed to software-only solutions after a hardware card crashed. Unless you are going to buy two of the exact same RAID card (one as a hotspare), or unless performance is a big deal (which it shouldn't be on a backup system I would think), software-only solutions are the way to go. I complement this with off-site continous backups of irreplaceable data (about 200GB) to CrashPlan. I really wanted to use ZFS, but the Linux support isn't that great, and also I don't think it's possible to remove drives from ZFS arrays. Both of those were deal killers for me. In any event, LVM+XFS has worked out great. XFS is a very stable file system and has given me no trouble.