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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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Posted on Sep 2, 2020 9:09 AM

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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5 replies

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

WD 5 Tb external drive won't mount

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