rsync, ionice, iotop

c’t-Archiv, 23/2011, Seite 154: “Rsync zwingt Linux-Server in die Knie”.

The above article (in German) is about using rsync together with ionice (like “nice” but for I/O load).
You can watch your processes’ I/O load with iotop (like “top” but for I/O load).