Announcement: Upgrade to macOS Mojave

With features like Dark Mode, Stacks, and four new built-in apps, macOS Mojave helps you get more out of every click. 
Find out how to upgrade to macOS Mojave >

Looks like no one’s replied in a while. To start the conversation again, simply ask a new question.


Question: After High Sierra Upgrade, my usb drives disconnect at night

After High Sierra Upgrade (10.13.1) from Sierra on my iMac (late 2013 version), my usb drives used for TimeMachine become disconnected / inaccessible at night and TimeMachine backups fail. . The drives are Western Digital My Passport for Mac 2T drives. In the morning, I unplug the drives, plug them back in, and everything works again, and TimeMachine starts a new backup. This never happened before the upgrade, and started happening the 1st night after the upgrade. Ran disk utility and the WD drive tool, and both say the disks are fine. So, has to be related to the upgrade.

I think this is related to Energy Saver Sleeping. In Energy Saver settings, I have checked

- Put hard disks to sleep when possible

- Wake for network access

- Enable Power Nap

Schedule is set to "Sleep everyday at 1am."

All the TimeMachine failures happen after 1am. Last backup is around midnight and then nothing until I reconnect the drives. I will try turning off the "Sleep everyday at 1am" to see if that removes the issue, but this was never a problem before. Seems like a bug was introduced in High Sierra in Sleep in handling USB drives.

iMac, macOS High Sierra (10.13.1)

Posted on


Page content loaded

Nov 19, 2017 10:27 AM in response to mdguzzi In response to mdguzzi

Disabling nightly sleep has worked around the issue. So there's something that's been introduced / changed in High Sierra that breaks the interaction of sleep and usb drives.

Nov 19, 2017 10:27 AM

Reply Helpful

Dec 11, 2017 1:49 AM in response to mdguzzi In response to mdguzzi

Something similar is happening with my system. Almost new iMac + Lacie 1Tb drive and 10.13.2

Here "Prevent sleeping" is ticket and "Enable Power Nap", but it still manages to unmount and remount the drive in the night. Backups often stopped.

Dec 11, 2017 1:49 AM

Reply Helpful
User profile for user: mdguzzi

Question: After High Sierra Upgrade, my usb drives disconnect at night