External Hard Drive Will Mount on One Mac, but Not the Others?

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External Hard Drive Will Mount on One Mac, but Not the Others?

I have three different Macs, a Mac Pro (Late 2013), a MacBook (2017) and a MacMini M1 (2020). All are running Mac OS 11.3.

Enter my Western Digital 3TB external USB3 hard drive. It will mount and run perfectly well on my Mac Pro, but not on my MacBook or MacMini, and this problem only seemed to crop up recently. Even with the Disc Utility, I can see no evidence of the drive. I have connected the drive directly to the Macs' USB ports (avoiding the dongles I have on both machines to rule them out of the equation), but still nothing.

The only other thing that stands out in my mind is that I initially formatted the drive on the Mac Pro, under an earlier Mac OS. But this would not explain why only recently it started to refuse to mount on the other two machines. This is baffling. Any pointers out there as to where I could find a solution?

Mac mini 2018 or later

Posted on May 8, 2021 1:02 AM

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Answer 1

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Raoul_Duke Author

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61 points

May 8, 2021 5:33 AM in response to Barney-15E

"In Finder, if you Go > Computer, does it show up there?"

No, that is one of the first things that I tried; no dice. Like I said, not even the Disk Utility can see the drive. Thanks anyway!

BTW, I should mention something by way of example; I connected a simply ancient (10+ years old?) 1TB hard drive into the MacMini via an unpowered USB3 dongle, and it worked without a hitch. I think we are slipping into the world of witchcraft here...

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Answer 2

Raoul_Duke Author

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May 8, 2021 10:47 PM in response to Old Toad

Well, I could not try another cable for the simple fact that I did have another one, as it's one of those special broad, flat, bi-segmented plugs that inserts into the hard drive. However, once I obtained a second cable, I am ashamed to say it worked on all three Macs! One can well imagine a hard drive mechanism failing over time, but a cable? Anyway, thanks for the assistance. The simplest and most obvious solutions are usually the best, if you have the needed gear, yes?

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Answer 3

Barney-15E

Level 10

116,992 points

May 8, 2021 9:59 AM in response to Raoul_Duke

The software isn’t on the drive. You would have installed it on your Mac, so it doesn’t seem it is the problem, either.

I don’t know what is wrong.

Try booting into safe mode and see if it

mounts.

https://support.apple.com/en-us/HT1455

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Answer 4

Barney-15E

Level 10

116,992 points

May 8, 2021 2:36 AM in response to Raoul_Duke

If it is bus powered, it may be trying to draw too much current from the port, causing the port to reset. Do you have a powered hub to connect through?

If it is a spinning drive, you can normally hear or feel the drive spin up, then spin down, repeating that process if it is drawing too much power.

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Answer 5

Raoul_Duke Author

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61 points

May 8, 2021 3:04 AM in response to Barney-15E

Yes, I have tried both through a powered hub (two separate ones, in fact) and directly into the USB ports of the misbehaving Macs. And, yes, I can tell when an external hard drive is not receiving enough juice from its port, with its distinctive, rhythmic "click, click, click...", and with these Western Digital drives, when their LED simply flashes on and off with a regular beat, something is amiss with the interface to the CPU. Irritatingly, the LED my 3TB drive illuminates itself steadily as if connected.

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Answer 6

Raoul_Duke Author

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61 points

May 8, 2021 6:38 AM in response to Barney-15E

With the drive connected directly to the only USB-C port of the uncooperative MacBook, under System Information, this is what is listed under USB:

USB 3.0 Bus:

Host Controller Driver: AppleUSBXHCISPTLP

PCI Device ID: 0x9d2f

PCI Revision ID: 0x0021

PCI Vendor ID: 0x8086

To my knowledge, there is no NTFS software on the hard drive. I did format it purely for Mac use when I first purchased it.

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Answer 7

steve626

Level 6

11,573 points

May 8, 2021 10:18 AM in response to Raoul_Duke

Raoul_Duke wrote:

"In Finder, if you Go > Computer, does it show up there?"

No, that is one of the first things that I tried; no dice. Like I said, not even the Disk Utility can see the drive. Thanks anyway!

BTW, I should mention something by way of example; I connected a simply ancient (10+ years old?) 1TB hard drive into the MacMini via an unpowered USB3 dongle, and it worked without a hitch. I think we are slipping into the world of witchcraft here...

I think, based on the information you have presented, that the drive that won't mount is defective or failing. It won't mount on 2 out of 3 computers, that implies something is amiss with the drive, it may be marginal, e.g. maybe barely able to work on that one computer that might be supplying slightly more or less power than the others. Also the Mini can mount other drives (or at least one other drive), so that implies that the Mini is ok.

I guess it is POSSIBLE that 2 out of 3 Macs are suddenly going bad in the same particular way but that is less likely than an inexpensive external mechanical drive simply failing. The simplest explanation is usually the most likely.

I would mount the problematic drive on the one Mac that can see it and copy everything off for safekeeping. I would stop using that drive, they all wear out at some point. If you are really interested, you could run DriveDX on the drive to see what it says about the condition of the drive.

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