I have an external USB drive from LaCie that is connected to my MacBook Pro – almost all the time. So whenever I don't use it for a few minutes, it powers down. That means, it takes a few seconds to spin the disk up again if I need it.
Sometimes, other applications wake the drive up even when I don't want to, causing the applications to hang (i.e. wait for the drive).
How can I increase the time before the external drive powers down?