When I received this note, my thought was “with Apple Core Rot worsening, and with OS X Yosemite the buggiest OS X release ever, this might be a real issue rather than an isolated incident”.
Have you run into the new bug where Yosemite shits the bed if it goes to sleep with a USB HD attached? Upon wake, Yosemite displays a warning that the drive was unplugged without being safely unmounted. The drive icon is still on the desktop and the entry in /Volumes. But no amount of dragging the icon to the trash, command-line tricks, or Finder restarts can remove the icon.
The real fun happens when you try to reboot the computer—it hangs after quitting the running apps. The only option is then to power-cycle the machine.
I'm getting this on my work machine, a refurb Late-2013 rMPB purchased last month. Searching turned up a couple threads about this on Apple's own discussion forums.
MPG: yes this is happening to me too, every day now for 3 days on a 2013 MacBook Pro 9,1 (after overnight sleep), but also once while in use so that raises a question mark. On this system, the drive is the 480GB OWC Envoy Pro EX direct-connected to the USB3 port of the laptop. It’s hard to believe that a drive that has worked flawlessly for nearly two years is now bad.
I’ve swapped the cable and drive to see if this repeats. And I’ve put the 480GB Envoy Pro EX on a late 2013 MBP Retina as another test. Monitoring both now.
Apple replaced my iMac due to this issue, 6 weeks of going back and forth. I had two OWC Mini Stacks and two Buffalo Drive Station DDR (HD-GDU3) drives attached and after numerous events the Buffalo drives became unmountable.
Same exact issue: come out of sleep and the drive was either missing (icon and all) or was not available even though it should up in disc utility. Apple sent me a thunderbolt LaCie 3 TB drive as reparation, and then after weeks more they replaced the 2012 iMac with a new 2013 5K. It isn’t affecting my Thunderbolt drives and I keep the USB3 drives offline until I need them.
To date I have not had resolution from apple, this all started with in a week of upgrading to 10.10.
MPG: A little birdie tells me that OS X 10.10 has introduced subtle new issues into Thunderbolt (bugs). It would hardly be surprising that USB3 is also damaged by the same Apple incompetence in QA (quality assurance and regression testing). Ten months ago the file system was broken in one ugly way (and more), and that’s stuff that worked for a decade or more. More Apple Core Rot.
Steffen K writes:
It’s not only USB-Harddrives that get unmounted. I have a Seagate FreeAgent GoFlex Drive connected to a late 2009 iMac (iMac11,1) by Firewire800 as Time Machine drive. It’s a 2.5“ drive that gets powered by Firewire.
Exactly the same thing happens form time to time after waking the machine up. The system then tells me that the drive was unmounted incorrectly.
What makes this quite interesting is the fact that the drive has worked fine prior to 10.10. And that the drive makes clicking noises after such an unmount. It’s almost like the drive has a short power failure when Yosemite is waking up.
MPG: sounds like a threading/timing error newly introduced at some common level in the I/O kit layer. But it could relate to power also.
Mark W writes (23 Sept 2015):
I never had this problem before upgrading to Yosemite. Now that I upgraded to Yosemite last week, suddenly I have this problem. I have made no hardware changes whatsoever. Just letting you know. Thank you for this blog post: It helps keep me from feeling that I’m crazy.
MPG: I’ve had additional issues on my Mac Pro, but only sporadically, and sleep not even involved.