I’ve administered this OS, which for us was used to develop images on plates for printing. It ran atop ATT UNIX and had to be “defragged” every now and again to regain contiguous space back. This process involved backing up the system to 250MB QIC tapes (twice for two sets of tapes), wiping the disks and then restoring the data from tape. This was an all-weekend process and really sucked if a tape broke, but that’s why there were two sets and scotch tape can work in a pinch when the other tape is bad.