Comment 41 for bug 1194608

FYI, when you unbind the scsi disk driver by writing the 1 to the delete knob in sysfs, it takes care of issuing the synchronize cache and start/stop unit commands. You can see this in dmesg. You mentioned the usb mass storage driver, which I would not have thought of. I'd bet that is the issue. My guess is that most drives appear to work because they shut off their LED when given the STOP UNIT command when the scsi disk driver unbinds, but if the usb mass storage driver is still bound, some drives decide to keep the LED on.