DDS2 is 8 GB per tape compressed (4 GB native).
But watch out: you'll need to source a cartridge magazine in order to use the changer!
Feh, I did not see the DDS2 part. (Yeah, it is probably part of the title.)
These days I have DDS2 drives laying around, though I am using DDS3 and DDS4 for my stuff. DAT72 is just too expensive for my tastes right now. (I think I actually have a DDS1 drive in my box-o-tricks.)
I have always been a fan of the auto-loaders. I guess mostly for the neat factor.