Cant write external disk with exFat or Mac OS Extended FS

After you bought it, did you completely erase/format it, before you began to use it?

If not, there may be "support software" on it from the manufacturer, Which can be trouble afterwards (examples: most LaCie drives, Seagate drives, etc).If you have acopy of everything, do the erase/format APFS-not encrypte-Guid partition map; then copy back the data. Guid is necessary, the (restricted) Master Boot Record leads to problems.

Assuming the diks are correctly formatted, either exFat or Mac Os Extended (journaled): they should be readable and writeable as before in all HighSierra and Mojave versions.

When they are SSD make sure that Mojave did not mess with the format.

If you have a copy of the data just reformat with DiskUtility.

If you do not have a copy, read the files in your friends mac first, then format.

I answered this... but something went wrong.

"Assuming the diks are correctly formatted, either exFat or Mac Os Extended (journaled): they should be readable and writeable as before in all HighSierra and Mojave versions. When they are SSD make sure that the FileSystem is not corrupted, or reformat in exFat or Mac Os Extended (journaled): if you do not have a backup of the data, ask your friend to meke a backup, then format, then put the data back from your friends backup.

Without you knowing the disk was formatted to APFS while upgrading to version 4 of HighSierra I suppose, or during your "experiment" with Mojave. There is an unofficial way to upgrade the OS without the APFS conversion, btw.

It certainly looks as if the disk is dead or dying.

I propose to download DriveDx from binaryfruit.com.

Use it and see if it can comment on the status of the disk.

Thanks for feedback.

Yes, I formated and it worked for about 6 months. Then suddenly it became read only along with all the other disk (afps or Mac extended) connected via USB.

I formatted again at least 3 more times (all formats) with no success: I believe that there is an operating system process that checks regularly USB connected disks and set it to read only. In fact when the only time that sudo mount -u -w command worked (I was able to copy about 300 GB of files on it), after a while, doing nothing and without unmounting or ejecting the disk became read only by itself !!!

Mistery of MacOS !!!

Sometimes the last post is invisible, if you ever see a post that's just a period, that's what many do to force the issue.

😎

I have exactly the same and its not a disk format issue:

Your disk is APFS formatted.

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thanks for keeping the message stream coming.... It is already a bit better today here.

Yeah it is better, yesterday I replied to 2 topics that had 0 replies & showed no replies... I replied & as soon as I posted 2 previous replies showed up from hours ago.