/n/mon/mnt/sda9/Downloads/Plan9/mroot-linuxemu.tbz2
how is that mounted ?
you've got two issues, how the tbz2 get to plan9 and then how long it takes to unzip
try % cd % time cp /n/mon/mnt/sda9/Downloads/Plan9/mroot-linuxemu.tbz2 . % time zxf mroot-linuxemu.tbz2 so we know what it is you're timing