M4 Mac Mini keeps disconnecting SSD drives. Time Machine Back Ups now failing. Solution?

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101 points

M4 Mac Mini keeps disconnecting SSD drives. Time Machine Back Ups now failing. Solution?

I have a 2024 Mac mini M4 running Sequoia 15.6.1.

When I purchased this new a few months back, I kept having issues with my 3 External SSD storage devices getting disconnected. Someone on the forums told me this was a power issue (too much for the Mac mini to handle directly plugged in), and told me to buy a powered hub for the external hard drives. I did that and everything had been working fine.

Now, fast forward months later, seemingly out of the blue I'm having the same problem, plus one with Time Machine.

My external SSDs keep giving messages that they were disconnected. They do appear back on the desktop without me rebooting. I'm also having an issue with Time Machine saying it could not back up because it encountered a problem but no other info. When I watch the back up, it hits a point where it says "skipping" and then it gives the message.

I tried plugging one of the SSDs directly into the Mac mini and leaving two in the powered hub. I received the same message from the one plugged in to the Mac. So I switched them around again and this time I received an error from the one plugged in to the Mac AND one plugged into the hub.

Seems more of an issue when this time off the screen. I have turn disks to sleep off.

I've made sure all cords are firmly pushed in.

Not sure what I should do to further diagnose the issue or why this is happening. Any advice? Thank you.

Posted on Sep 2, 2025 05:46 AM

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Answer 1

den.thed

Level 10

88,654 points

Sep 2, 2025 08:04 AM in response to Ramblinmanva

What external SSD's..?

(brand, model and type of USB connections)

What powered external hub..?

(brand, model and type of USB connection)

If you are plugging the hub and SSDs into the Mac mini's USB-A ports..?

Try moving one of the SSDs over to a TB/USB-C port using USB-C to USB-A adapter.

Or optionally move the hub and two SSDs over to a TB/USB-C port using USB-C to USB-A adapter.

for some examples:

USB-C to USB Adapter - Apple

https://www.amazon.com/dp/B07PDLQ555/ref=sspa_dk_detail_0?

https://www.amazon.com/dp/B08Z768LCW/ref=sspa_dk_detail_1?

https://www.target.com/p/philips-usb-c-to-3-0-usb-a-female-adapter/-/A-79804275

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Answer 2

Old Toad

Level 10

214,230 points

Sep 2, 2025 03:22 PM in response to Ramblinmanva

Are the unmounting of the drives tied into sleeping the Mac? If so don't sleep the Mac. User the Screensaver to turn off the monitor after a specific amount of time for the screensaver. Many users have tied the sleeping in with a variety of issues with the newer Macs.

I have a Mini M4 with 2 drive docs and a USB A hub, all self powered, and a couple of bare SSDs with a USB C to SATA adaptor and never had any unmounting issues. I don't sleep my Mini.

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Answer 3

Ramblinmanva Author

Level 1

101 points

Sep 2, 2025 05:07 PM in response to Old Toad

Thanks for the response. I do not have my computer to go to sleep. Turned off when I first got it. Screen saver activates after 1 hour. I was hoping it was the sleep setting but I already had it turned off. This was working for months and I had changed nothing (that I know of) in my set-up that would have caused it. I had a previous post here when I first got it and folks told me the Mac didn't have enough power for the 3 external drives. Since adding the powered hub, I had been good. Thx.

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Answer 4

Ramblinmanva Author

Level 1

101 points

Sep 2, 2025 05:10 PM in response to den.thed

I have three San Disk SSDs. Two are for files. One is for Time Machine backups. Each one is a 4tb drive.

I use the cords that came with each device. USB3.

I have an OWC powered hub that someone on here recommended. It has three USB-C ports. I had been running each drive on one of those ports with no problem until now. I tried plugging one of the drives straight into the Mac mini and leaving 2 with the hub. Didn't make a difference.

I'll check out the other links. Thank you.

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Answer 5

den.thed

Level 10

88,654 points

Sep 2, 2025 05:57 PM in response to Ramblinmanva

That is good info, thank you.

1) Double check the OWC's external power supply to make sure that it is plugged in and working.

2) Move one SSD or the OWC hub over to one of the Mac mini's TB/USB-C ports using one of the suggested adapters.

The reason that I am suggesting that, is because the Mac mini's TB/USB-C ports can supply more power than it's USB-A ports.

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Answer 6

Ramblinmanva Author

Level 1

101 points

Sep 3, 2025 05:29 AM in response to Ramblinmanva

I'm the OP with an update and a related question.

Trying to diagnose things as everything had been working, I decided to run Disk Utility First Aid on each of the three external SSDs. Two checked out fine but one of them reported something about a corrupt file. I tried to delete files one by one but it was taking too long to test that way. After making sure everything was backed up, I decided to erase and re-format that drive and re-connect everything back up. It's been about 14 to 20 hours I guess since that time and I've not had another crash.

Could a corrupt file on one external SSD cause all three devices to crash? And cause a problem with a Time Machine backup on one of those drives? I had been getting "skip files" and an error on the Time Machine back up. That is no longer happening and it's backing up. I did end up re-formatting the time machine drive to as part of the process.

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