USB 3 drive falls asleep and hangs system
I have a USB 3 drive and I notice that when accessing files on my internal drive (that is, not the USB 3 drive) it sometimes needs to wake up. I hear it whirring up to speed and it takes about 5 seconds while the entire system hangs until it comes online and then everything goes back to normal. This happens while I am already actively using the system. Any idea why and how to stop this?
By the way, the drive was in a Lacie enclosure, but I moved it to a new USB3 enclosure myself. It is listed in Disk Utilities as a SAMSUNG HD204UI. It's 2TB and 7200rpm. I also have a WD drive in another USB3 enclosure as a Time Machine backup. It doesn't seem to be causing the issue.
iMac, OS X Mavericks (10.9.1), 3.4 GHz, Fusion drive