External hard drive freezes main thread in OS X Lion Randomly my external hard drive freezes the main thread in OS X as it's waiting for I/O when in power-save mode. Everything is stuck. It freezes for about 1-3 seconds.

Is there anything I can do besides unmounting the hard drive (used for storage and Time Machine)? Any suggestions to what OS X is actually is doing with the drive? I've checked; it's not always Time Machine.
This is somehow one of the most frustrating things around for me as well.

I want to allow my mac to spin down the hard drives when they are idle, but this makes for long delays (on the order of 3-5 seconds normally and on occasion even longer).

Quite simply, allowing those connected devices to block the fseventsd and other system level daemons means putting up with long delays when you don't really want them.

You can and should turn off the sleeping drive to prevent intermittent slowness.