My external hard drive (seagate barracuda with good SMART status insidev erbatim 4TB store 'n' go) has 3 main partitions:

1) ntfs
2) hfs+ for time machine backup
3) exfat to transfer files between windows and mac

Windows shows correctly all partitions without errors or warnings. Mac shows only 1 and 2. The third is occupied by fsck_exfat which started automatically every time I plug the hard drive in. So I force close that process, go to terminal, digit "sudo fasck_exfat -d disk1s2" and press enter. After a while it shows:

0 clusters were marked used, but not referenced
0 clusters were marked used and CLUST_BAD
0 clusters were marked free, but referenced
** Rechecking main boot region.
** Rechecking alternate boot region.
Mark volume clean?

Type yes but then:

fsck_exfat: Could not update main boot region: Bad file descriptor.

After that the disk is now visible in finder in ready only mode. I have already formatted 2 times this partition but the result is the same.

  • same problem with WD Element, exFAT on whole partition of a 4TB HDD. maybe mac does not handle exFAT that well.. Did you solve the problem ? My OS : 1.9.5 . Tried "sudo fsck_exfat -y disk1s2" multiple times (grant yes to solve problems), same results. "fsck_exfat -q disk1s2" report FILE SYSTEM DIRTY, but that HDD is able to be read and written.
    – user305883
    Mar 24, 2019 at 8:42

1 Answer 1


Try to avoid using exFAT (or FAT) on storage with DRAM cache. exFAT does not support journaling or any other feature that protects the filesystem from corruption in case of unexpected power loss during write operation. This can lead to files, folders or the entire filesystem becoming inaccessible.

I would give using chkdsk on Windows a shot. For drive G: that would be chkdsk G: /f, or, to include checking for physical errors, chkdsk G: /r.

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