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ExFAT format issue

Active Member

I have a new Samsung SSD (4 TB).


I formatted it in ExFAT on Windows, then when connected to Mac it comes up as read only - the drive can be read but no data can be added or changed, it can only be written to on Windows.


I formatted it again in ExFAT on Mac, then when connected to Windows it comes up as read only - the drive can be read but no data can be added or changed, it can only be written to on Mac.


I've used at least 10 other hard drives (conventional HDs not SSDs) formatted in ExFAT and they've always worked across Windows and Mac with full read-write functionality.


Can anyone shine any light on why this SSD seems to have to this issue? And more importantly how to solve it?

Topic starter Posted : 17/11/2020 7:53 pm
Community Legend

You are not providing any meaningful detail, nor any result of the basic troubleshooting in such cases, i.e. diskpart output in Windows and diskutil output on the Mac. (BTW which EXACT version of the operating systems are them).

Set apart the - possible even if the device is brand new - possibility that the SSD (BTW which EXACT model is it, how EXACTLY is it connected to the one and the other computer) is defective, the read-only status may be connected to mount policies, to specific limitations (on the bus/connection)  or to settings on the actual disk/device.

On Mac, check:

On Windows, you can try clearing the read-only volume attribute and run chkdsk:

Another basic check is to try another disk drive, with both computers, now, as - since the last time you used one of the at least 10 other disks - *something* may have been changed (by updates or by some program) in the settings of the one (or the other, or both) computer(s).





Posted : 18/11/2020 9:46 am
Community Legend

Sounds like a potentially interesting issue of forensic interpretation. Suspected disk holder claims he can't write to the disk, while analyst find no problem whatsoever, and concludes that the suspect may be economical with truth, and draws conclusions accordingly.

Please post any tested and verified explanation ... or even just additional data points if nothing else.  The details requested by Jaclaz are such data points.


Posted : 18/11/2020 11:50 am
Senior Member

It is a slightly wild guess - because exFAT should compatible - but does the drive have a 4KB sector size?

Have you made it work on other 4TB drives, or 4TB SSD drives?

This post was modified 4 months ago by mscotgrove
Posted : 18/11/2020 12:17 pm