I have a 1TB Western Digital external hard drive that I use for Time Machine backups, and recently my iMac has started to randomly eject the hard drive, preventing backups. It tends to happen while the display goes to sleep, but I have my Energy Saver settings set to not put the hard drives to sleep, and the computer is set to never go to sleep.
To correct the issue, I pull the USB cable on the drive and then re-attach it. I'm wondering if this is just a bad drive that I need to return or if this is some kind of larger issue.
Best Answer
Someone reported a similar issue on an Apple discussion forum:
Another poster in the same thread commented:
You should first back up that drive before anything else. Contact WD to see if they can send you a new USB cord. It's a good idea to run some diagnostics on the drive to confirm that there are no disk errors. Testing on another computer would also be a good idea to narrow down to see if the issue is isolated to your machine or the drive.
If the drive is failing, you'll need to return/exchange it.