WD 5 Tb external drive won't mount

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Level 2

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WD 5 Tb external drive won't mount

Hi all. I have a new 5Tb WD My Passport Ultra external drive. I formatted it in exFat in order to read/write in MacOS environment. It works fine on a PC. When I try to use it on my MBP running Catalina 10.15.6 it won't mount. Disk Utility First Aid shows no errors. The disk appears "grayed out" on the left in the utility. When I try to mount the disk I get the following error message "Could not mount "My Passport". (com.apple.Diskmanagment.disenter error 49223.)

Any thoughts? I've googled the error message and looked in this forum but can't seem to find anything that helps!

Posted on Aug 27, 2020 6:33 AM

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Answer 1

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Boating Dave Author

Level 2

146 points

Sep 2, 2020 9:09 AM in response to DanielleM182

Yes thanks I had used the utility. It showed no errors. Ultimately I reformatted it in exfat on the Mac and then it became visible. Odd that the original exfat formatting on the pc Was not accepted by macos

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Answer 2

Aug 28, 2020 9:58 AM in response to Boating Dave

Hey Boating Dave,

Thank you for using Apple Support Communities!

We hear that you're having trouble with your external storage device on your MacBook Pro. We'd like to help out.

Try repairing the disk here:

Repair a storage device in Disk Utility on Mac - Apple Support

Let us know if this helps.

Cheers!

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Answer 3

HWTech

Level 9

55,946 points

Aug 28, 2020 8:12 PM in response to Boating Dave

Did you use Windows or macOS Disk Utility to format the drive? Windows can use block sizes which macOS does not recognize so you either need to have Windows use a block size compatible with macOS or use Disk Utility to erase the drive instead.

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Answer 4

HWTech

Level 9

55,946 points

Sep 4, 2020 6:02 PM in response to Boating Dave

Someone posted a link about the issue on here a couple years ago and I believe their link may have contained some of that information, but I'm not sure. Larger drives require larger block sizes (allocation units). I'm not aware of any Apple documentation (or even non-Apple documentation) except for random posts online where users have experimented in discovering compatible block sizes.

Here is one older article which mentions 128 KB:

https://joshuatj.com/2015/05/13/how-to-format-your-hard-drive-hdd-for-mac-os-x-compatibility-with-the-correct-exfat-allocation-unit-size/

This post from 2018 mentions a 1024 KB allocation unit size:

https://apple.stackexchange.com/questions/293390/macos-cant-mount-exfat-external-drive/336633#336633

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Answer 5

Boating Dave Author

Level 2

146 points

Sep 2, 2020 9:10 AM in response to HWTech

Yes this was the issue I think. Does anyone know what the block size that is compatible with Macos is?

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WD 5 Tb external drive won't mount

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