I got a new 512Gb SD card for my Samsung Galaxy J7 Crown and started experiencing problems when attempting to load my music folder onto it.

  1. Unmounting the card and inserting into a Win 10 computer, copies more than two directories deep would fail, so I broke the task up into transfer units that the computer could handle. ("Fail" in this case means "refuse to perform, without error message or indication of the source of the problem")
  2. Up to a certain point, transferred files would appear and be accessible. However, when roughly 1/3 of the files were transferred, all files would be erased. The folders would remain, but they would all be empty. This was true regardless of whether the SD card was inserted in the Win10 machine or in the phone.

Inserting the card into the Win10 machine and running chkdisk indicated no problems.

Reformatting the card as exFAT using the Win10 machine led to the same problems described above.

Inserting the card into the Win10 machine and reformatting as NTFS solved both problems. However, Android will not recognize NTFS.

I am currently reformatting the card using the phone to see if that solves my problem. If not, my plan is to use my Linux box to format the card with FAT32 and live with the 4GB/file limit.

Obviously I'd prefer a different solution, either "exFAT that works", NTFS or ext4.

Has this problem with exFAT on high capacity cards been observed before? It's sure not a subtle matter of a slight performance difference: it clobbers all the files that it makes you jump through hoops to copy onto the device. I would appreciate any advice on how to make this card work: whether that's how to get Android to recognize a filesystem which does not exhibit these issues or how to fix the issue with exFAT.


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    Cards of that size are still expensive and therefore are often forged (card clains to be of size 512GB but has internally only 4GB or so). Please before using such a card make sure it is genuine by testing it using h2testw or F3 – Robert Jun 12 '20 at 14:38
  • @Robert 4GB is the maximum file size limit on fat32 partition – alecxs Jun 12 '20 at 18:10
  • @alecxs My comment was on the failed test on the PC using ExFAT. The 4GB I mentioned was just a random value as you never know how much flash is really in a forged USB stick. – Robert Jun 12 '20 at 18:36

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