I have a WesternDigital external(usb3) 5TB hdd that keeps mounting as readonly on the mac every time I reconnect it.

The drive was formatted ExFat with diskUtil and is only about a month old.

I've run sudo fsck_exfat -dy /dev/rdisk3s1 several times, I keep getting results like this.

0 clusters were marked used, but not referenced
0 clusters were marked used and CLUST_BAD
21 clusters were marked free, but referenced
** Rechecking main boot region.
** Rechecking alternate boot region.
Write     offset = 0x000006040000  length = 0x040000
fsck_exfat: Couldn't write 262144 bytes at offset 100925440, errno 9: Bad file descriptor

I can remount the drive with sudo mount -u -o rw /Volumes/Clients and it seems to work mostly fine (found one corrupt file, but since theres tens of thousands of files, I cant check them all).

How do I troubleshoot the drive further?

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  • Welcome to Ask Different. If you have access to a Windows computer, you may want to check the drive with chkdsk, see docs.microsoft.com/en-us/windows-server/administration/… for more information. If you don't, I'd recommend that you back up the contents of the drive, reformat and restore it. If the problem comes back, the drive may be defective. – jaume Apr 9 at 10:07

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