Pretty much anything, though storing backups to Amazon S3 is easiest because authentication and key management are automatic. You just need to run:

tklbam-backup

But you can also backup to any storage target supported by TKLBAM's back-end Duplicity including the local filesystem, NFS, Rsync, SSH, FTP, WebDAV, Rackspace CloudFiles and even IMAP.

The local filesystem is one of the easier storage targets to use because you don't need to mess around with authentication credentials.

So assuming you want to store your backup at /mnt/otherdisk:

tklbam-backup --address file:///mnt/otherdisk/tklbam/backup
tklbam-escrow /mnt/otherdisk/tklbam/key

And restore like this:

tklbam-restore --address file:///mnt/otherdisk/tklbam/backup \
               --keyfile=/mnt/otherdisk/tklbam/key

Not as easy as the Hub-enabled "automatic" mode, but still vastly easier than your conventional backup process. The disadvantage is that you won't be able to restore/test your backup in the cloud, or from a VM running in another office branch (for example). Also keep in mind that a physical hard disk, even a RAID array, provides much lower data reliability compared with Amazon S3.

For this reason we recommend users use local backups to supplement cloud backups (e.g., providing fast local access).