External drive used for Time Machine regularly disconnects

On my Mac mini m4, have been using an external WD Elements 2TB drive for Time Machine. After a while, it just disconnects. Unplug, plug back in and works for a few days, then disconnects.


The internet tells me the following may be the cause:

  • Cable
  • Mac doesn't like drives getting power over USB
  • USB hub
  • Pre-made external drives typically use the least quality drives


So to address all these potential issues, I replaced the above with:

  • New OWC Mercury Elite Pro USB 3.2 External Drive Enclosure
  • New Western Digital 8TB Red Plus NAS external drive
  • New USB-C cable
  • New Belkin USB-C 3.2 hub


The darn thing still disconnected every few days!


I have another external drive, a 2TB NVMe in an OWC Express NVMe enclosure, that never disconnects. But I don't want to use NVMe for Time Machine, especially when I need a larger drive.


Please help save my sanity.

Mac mini, macOS 15.5

Posted on Jul 11, 2025 08:54 AM

Reply
4 replies

Jul 11, 2025 09:53 AM in response to swingandmiss

You've done some great troubleshooting already. 👍🏽


Do you allow the Mac mini to sleep?

We very often see issues with the sleep feature. It's typically advised that you disable sleep as it's really unnecessary for these Macs. Simply allow the display to turn off after a period. This seems to alleviate the problem of drive disconnects.


Also, and this is just speculation on my part, but the NVMe drive may not disconnect because the ssd would react more quickly to power management commands than the rotational hdd. As such, if you allow drives to sleep when possible, then waking a rotational drive might be problematic. Of course there are many other reasons why the ssd doesn't dc.

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External drive used for Time Machine regularly disconnects

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