Even if he were paying me to use tarsnap I wouldn't use it for backing up 12TB.
I'd consider a backup solution that takes 3+years to make a full backup (or 4 months for a restore) to be of negative value to me...
(I wonder how many months I'd get away with uploading 300GB/month before my "unlimited" ADSL plan hit me with it's "acceptable use" disclaimers? Given that I'd be using 100% of my upload bandwidth to take this 3 year backup, I suspect the cost of 2 identical drives to make local backups would probably be cheaper than the network costs of sending it to tarsnap!)
I'd consider a backup solution that takes 3+years to make a full backup (or 4 months for a restore) to be of negative value to me...
(I wonder how many months I'd get away with uploading 300GB/month before my "unlimited" ADSL plan hit me with it's "acceptable use" disclaimers? Given that I'd be using 100% of my upload bandwidth to take this 3 year backup, I suspect the cost of 2 identical drives to make local backups would probably be cheaper than the network costs of sending it to tarsnap!)