So I have an OWC Mercury Elite Pro Mini external hard drive that is connected to to my Macbook Pro (2011) via Firewire 800. It's powered through the Firewire bus and I have another external hard drive that is a G-Tech 2tb daisy chained from it. The G-Tech one is not bus powered and used for backing up my Macbook Pro's internal drive as well as the OWC drive, so I only turn it on once a night to back up. I've been using it like this for about a month until two nights ago when the OWC drive spun down whenever I turned on the G-Tech drive. I wouldn't get a message about it ejecting improperly, so I think the firewire bus just suddenly can't supply enough power to keep it spinning while the other one is connected. I've tried daisy chaining the OWC drive with another external firewire drive and this does not happen, only with the G-Tech drive. If I plug the G-Tech's firewire cable into the OWC's even without the G-Tech powered on it spins down now. Is the G-Tech drive trying to power itself from the firewire bus? I've rest the SMC and PRAM on my computer and nothing's changed. I'm guessing the problem is probably not with the OWC drive as it only does this with the G-Tech drive. Has anyone had an experience like this? Any diagnostic tests to determine whether it's my MBP's firewire bus or either of the external hard drives that's causing this? I'd appreciate any help or ideas to figure out what's wrong here.