Even though you have over a terabyte of space left, you may still not have enough space left to store two copies of the duplicated file on separate drives. This can happen bacause the storage algorithm Windows Home Server V1 uses tends to prefer to put new
files on disks that are already closer to full. This algorithm struggles when you use duplication and add disks one at a time (which I presume is what you've been doing), because Windows Home Server doesn't go back later and move files off of full disks to
balance free space across all disks. So you can end up with one disk that's mostly empty, and all other disks mostly full.
As for what you can do, there's no supported way to force Windows Home Server to move files around. It will do so if a disk fills up completely, but that's not actually your situation; "completely" means dropping below a threshold, and one
BD rip is usually larger than that threshold. Options include using third party tools (there are a couple mentioned in this and other Microsoft WHS forums) and manually removing some files from your server until the ripped file will fit. (After which
you may have trouble getting those files back onto your server.)
I'm not on the WHS team, I just post a lot. :)
