Drive spanning and running out of space in this case go hand in hand. When a raid/merged directory runs low on disk space on the last listed drive, it should switch uploading to the next drive with free space. I discussed a number of issues associated with this (it's a hard problem to get right) so it's tricky. As a side effect of determining when to switch to the new drive it will handle a regular single directory mountpoint by just halting uploads and/or new directory creation.
It looks like warchive doesn't actively prohibit uploads or dir creation, but starts deleting stuff automatically. That's cool for people who want that done automatically, but even in the best of cases it doesn't understand raided directories and won't switch drives.
Unfortunately this is considerably harder than a 1hr solution and I pulled my first attempt from 6.3 just to get it out the door
