my setup...

Primary computer.
RAID 1+0 with 4 x 1TB drives (2TB of storage)
External Backup 2TB drive with Dmailer Backup with Livebackup (continuous backup with live changes)

File Server:
All Data backed up in a RAID 5 config with 5 x 2TB drives.

then remote backups...
Full backup from primary computer with liveback up to Backblaze.com
All final selects backed up to Photoshelter.com (this is the very last resort, if all my images get destroyed i will still have all my finalized hires jpgs)

Im a professional photographer, and my images are my livelihood. hence the multiple backup solutions.