Dave: I can't understand what all you're saying here. I know you're not around much/paying much attention (rightfully), but could you elaborate here?

The idea here was to back up each host to its own logical volume (all on the same physical disk). Thereby making it trivial to see how much disk space each host's backups are taking ("df" on that host's backup LV), and also effectively implementing backup quotas (so that a host can be guaranteed not to run out of backup space on account of another host using up too much backup space).

Not sure if it's worth continuing with this idea though.