Offsite backup, BUT without local copy of the data (with catalog)?
dnewcome: I know this thread is old, but I ran across it in a search.
I use a tool called dar (http://dar.linux.free.fr/) that is along the lines of tar, but with extra features for dealing with multi-volume backup sets and diffs easily.It lets you extract a catalog from the backup set that you can use locally as a checkpoint for doing diff/incremental backups.  The catalog is really small, mine is ~10Mb for hundreds of thousands of files.  ## here is the initial backup: backing up /nas to
  ## an archive set /mnt/usb/nas on a usb device
  dar -R / -c /mnt/usb/nas -g nas

  ## extracting the catalog from the backup and 
  ## saving it under my home directory      
  dar -A /mnt/usb/nas -C /home/dan/backup/nas-catalog

  ## I use the local copy of the catalog in my home folder 
  ## when doing diff backups to another mounted usb device
  dar -R / -c /mnt/usb/nas-diff -g nas -A /home/dan/backup/nas-catalog