I have a 4 TB LaCie RUGGED USB-C external hard drive, and when it's connected to my MacBook Pro (13-inch mid 2014) for a long time without being used, it stops working. I do allow drives to sleep when connected in the settings.

  • Icon remain on desktop, but trying to open it or ejecting it, causes Finder to hang.
  • When I unplug it, Finder unblocks
  • When I plug it in again, it’s working (for a while of course)
  • The drive is bus powered and does not have an external power source

I use this drive for Time Machine backups, but sometimes Time Machine fails to backup.

I’d like to isolate the issue to know if the Mac is the problem, the cable is the problem or the drive is the problem or I need to change settings.

Can I use a system log or Time Machine log to diagnose what’s happening?

  • Hi. I’m going to edit this. Please put a potential answer in as an answer. “Trying energy saver” is an answer - not an edit to the core question. Also - just edit things so it’s correct - the system shows who edited and when in the edit history. apple.stackexchange.com/posts/356779/revisions
    – bmike
    Apr 14 '19 at 16:45
  • 2
    @slm Please put your potential answers in as answers. Comments are for clarifying the question. I think we have a clear statement now.
    – bmike
    Apr 14 '19 at 16:48
  • @bmike Thanks for your edit. I added trying power saver as an answer.
    – Behdad
    Apr 14 '19 at 16:48
  • 1
    I’ve also edited out at least 4 side questions. One question per question is best. How to troubleshoot is great. All the potential avenues can be stand alone answers and help many people that have a disk not responding.
    – bmike
    Apr 14 '19 at 16:49
  • @bmike - will do, I didn't have a fully coherent A'er so didn't want to just give the OP a link w/o more details and evidence.
    – slm
    Apr 14 '19 at 17:23

I searched around and found out that there's an option in Energy Saver: Put hard disks to sleep when possible and it's checked on my Mac. You can see the option in the screen shot below: macOS Energy Saver options

  • 2
    Very good changes. I would potentially disable PowerNap as well while you chase down sleep/wake/disk arbitration issues. The battery shouldn’t affect things, but one thing a battery does do is act as a capacitor and even out bursts of energy demand that the charger won’t/can’t provide. If your Mac is powering this drive over USB - that might be a root cause of not enough energy to spin up - even if you are connected to a charger - the Mac still has to supply power to spin up a HDD in some cases.
    – bmike
    Apr 14 '19 at 16:51

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .