With a nearly full /usr filesystem, on a gconcat volume consisting of two 300gb drives and 1 500gb drive, using rtorrent (/usr/ports/net-p2p/rtorrent-devel) to allocate space for torrents that would cause the system to run out of space puts the system into a state where any filesystem activity will hang the process. How-To-Repeat: Fill up your volume to nearly full, have rtorrent create the files for torrents (note - not necessary to DOWNLOAD them) that would cause the volume to run out of space. Rtorrent should immediately hang, and any process attempting to access the filesystem will also hang.