Disksomnia

Disksomnia is kinda like the great grandson of Sleeper from the old Classic OS days who rebels against everything.

Disksomnia stops external disks from going to sleep. Video editing and sleeping disks are a bad mix, particularly if you have media spread across several external disks. If you've ever moved the playhead to another part of the sequence and stared at the spinning beachball while a disk wakes up then you'll know exactly what we mean! Disksomnia stops external disks from going to sleep (including those that ignore the Energy Saver setting to stay awake) by giving them a gentle poke every five minutes when Final Cut Pro or Final Cut Express is running. After installing and launching for the first time, Disksomnia is totally automatic and works invisibly in the background. There are no settings, no need to launch the app manually and best of all...no more sleeping disks.

A few people (including me) have had the exact same problem, where something in the firmware of an external -and sometimes internal- hard drive prevents it from listening to Energy Saver's preferences and it spins down every time there's lack of activity for what seems like 30 seconds.