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Multiple exFAT drives not mounting on MacBook

N

nateroe

macrumors newbie
Original poster
Sep 14, 2025
4
0
I have a MacBook Pro 16-inch Nov 2024. Apple M4 Pro. 24 GB memory. Sequoia 15.6.1 installed.

I have multiple exFAT formatted external hard drives that will not mount on my machine.

In the System Report under USD, I can see my drives.

One of them is a HHD:
Seagate Backup Plus
File System: exFAT
BSD Name: disk4s2
Content: Microsoft Basic Data

The other is a SSD:
Samsung T7 Shield
File System: exFAT
BSD Name: disk4s2
Content: Microsoft Basic Data

I have another exFAT formatted SSD that mounts perfectly:
Samsung T7 Shield
File System: exFAT
BSD Name: disk5s1
Content: Windows_NTFS

Both of the drives that won't mount on my MacBook mount perfectly on a Raspberry Pi with Ubuntu installed.

Any ideas what is causing this?
 
I am not prompted about allowing the connection for the drives that won't mount. The only place I am able to see that my MacBook detects these drives is in System Report > Hardware > USB.
 
Bigwaff said:
Allocation (block) size of the ExFAT partitions. macOS is very finicky and can only read ExFAT partitions formatted with block sizes 512 bytes to 1024 KB. Most likely the ExFAT disks that fail to mount use different block sizes. Here's a bookmark I saved which was very informative.
Click to expand...
From running 'stat -f /my/drive' on my Ubuntu machine, I get the result Block size: 131071 and Fundamental block size: 131072. I believe this means my allocation size is 128KB - well within the range you provided.

One additional note on the symptoms of the problem - one time I tried to mount this drive on my Macbook, it would not show up in Finder or Disk Utility, and then miraculously after 10 mins or so, it showed up in my Finder. I cannot get it to do that again...
 
nateroe said:
Both of the drives that won't mount on my MacBook mount perfectly on a Raspberry Pi with Ubuntu installed.
Click to expand...
As @Bigwaff says. The easiest solution is to format the drives with Disk Utility on macOS. And, of course, making a copy of the data using your Pi or a Windows PC.

nateroe said:
The only place I am able to see that my MacBook detects these drives is in System Report > Hardware > USB.
Click to expand...
You should also be able to see them in Disk Utility once you have the enabled the menu option View > Show All Devices.

nateroe said:
I have another exFAT formatted SSD that mounts perfectly:
Samsung T7 Shield
File System: exFAT
BSD Name: disk5s1
Content: Windows_NTFS
Click to expand...
That means the file system is NTFS (not exFAT). macOS is able to mount and read NTFS. If you want to write to it you need 3rd party software - e.g. from Paragon.
 
Open Disk Utility.app and check whether you can mount them manually there. I have some accessories that need this step because they don't mount automatically.
 
gilby101 said:
As @Bigwaff says. The easiest solution is to format the drives with Disk Utility on macOS. And, of course, making a copy of the data using your Pi or a Windows PC.


You should also be able to see them in Disk Utility once you have the enabled the menu option View > Show All Devices.


That means the file system is NTFS (not exFAT). macOS is able to mount and read NTFS. If you want to write to it you need 3rd party software - e.g. from Paragon.
Click to expand...
They will not show up in Disk Utility even with View > Show All Devices.

I am able to write to the drive with Content: Windows_NTFS without having downloaded any 3rd party software.
 
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