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Allocation Unit size and Mac OS

Recently, I plugged in a NT drive after installing Paragon NT for Mac. Paragon sees the disk but can't mount it It turns out that Macs are only able to work with certain allocation unit size. For example, if I plug in a exfat drive that uses the allocation unit of 4096 bytes, it won't mount. I had to change the allocation unit to 128K for the drive to mount. Any ideas?

Posted on Aug 17, 2021 10:46 PM

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Posted on Aug 18, 2021 7:08 AM

Thanks,

I have formatted exfat on the apple side to make them compatible. However, it would be nice to have some documentation on what the limitations are. I notice that the issue occur when the disk size is large. For example, I have no problems with thumb drives, but a 5TB exfat could not be mounted until you change the unit allocation size to 128K. I have even tried a smaller size like 64K, but 128K is apparently the min.


For NTFS I have ask Paragon. Again, it appears to be an issue with large disk size.

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Aug 18, 2021 7:08 AM in response to Matti Haveri

Thanks,

I have formatted exfat on the apple side to make them compatible. However, it would be nice to have some documentation on what the limitations are. I notice that the issue occur when the disk size is large. For example, I have no problems with thumb drives, but a 5TB exfat could not be mounted until you change the unit allocation size to 128K. I have even tried a smaller size like 64K, but 128K is apparently the min.


For NTFS I have ask Paragon. Again, it appears to be an issue with large disk size.

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Aug 18, 2021 7:11 AM in response to PRP_53

No Paragon software is the version that I downloaded as a trial. I plan to pay for it if it test out to be working. Out of the three I have tried to test:

  • Iboystore did not allow me to do a free trial because their server is down for a week. The latter lead me not to consider them since it implies they might be poor at maintenance.
  • Tuxera did not work for some reason.
  • Paragon so far seems to work pretty well except for the unit allocation. Initial test indicate that performance is actually pretty close to window's.
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Aug 18, 2021 7:13 AM in response to GentryAi

https://www.hcc-embedded.com/products/fat-file-systems/exfat


  • exFAT is a lightweight file system like FAT 32 (“lightweight” because it lacks NTFS’s extra features and their associated overheads).
  • exFAT supports greater file size and partition size limits than FAT 32. FAT 32 has a 4GB maximum file size and 8TB maximum partition size, whereas you can store files that are larger than 4GB each on a flash drive or SD card formatted with exFAT.  exFAT’s maximum file size limit is 16EiB (Exbibyte).
  • exFAT is compatible with more devices than NTFS, making it the system to use when copying/sharing large files between OSes. The Mac OS X has only read-only support for NTFS, but offers full read/write support for exFAT. exFAT drives can also be accessed on Linux after installing the appropriate exFAT drivers. Note, of course, that much older devices may only support FAT 32 and not exFAT.
  • exFAT is designated by the Secure Digital (SD) Card Association as the standard file system for high-capacity, high-speed SDXC cards


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Aug 18, 2021 1:58 AM in response to GentryAi

Usually it is recommened to format exFAT (GUID) on the Mac although I have had no trouble with exFAT disks formatted with the Windows 10 default.


About NTFS, I'd ask Paragon support.


I have had no trouble with the few NTFS disks on Intel Macs (i.e. read-only with Mac's built-in support) but AFAIR M1 Macs have had some issues with them.

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Aug 18, 2021 4:03 AM in response to GentryAi

Did the " Paragon " software come bundled with the external Drive. If yes, normally that version of Paragon is a modified version to work only with the Manufacturer drive. May need the full version directly from the Developer of Paragon

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Aug 18, 2021 7:14 AM in response to GentryAi

One other thing. I have notice that write performance from Mac to exFat is just plain terrible compare to Mac to NTFS using Paragon and from windows to exfat, so I am considering sticking with NTFS as a file format for exchange between window and Mac.

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Aug 18, 2021 10:56 AM in response to GentryAi

I done a few experimenting. Most of the drive seems to mount properly including ones as large as 1 Tb. What appears to be an issue is that when you have a large volume, the issue with unit allocation rears its ugly head. I actually have very few 5 Tb drives, so it was just bad luck that the first one I tried was a 5 Tb.


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Allocation Unit size and Mac OS

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