Bug with FAT and ExFAT File System

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Bug with FAT and ExFAT File System

Hi,

My USB stick (8 GB) was formatted using the ExFAT file system on my Macbook Pro Retina 13" running El Capitan 10.11.2. It was working fine up until yesterday, but today when I tried to mount it on a windows system, windows asked me to format it first and shows the drive capacity as 200MB. I found a discussion thread from a couple of years back on macrumours forum (http://forums.macrumors.com/threads/exfat-bug-urgent-help-required.1574098/, but with no solution.

The problem could be with the meta data. as the created date shows up as "January 1, 1970 5:30 PM".

The USB works fine on my mac with the ExFAT and FAT filesystem, but doesn't work on Windows. It also runs fine on the HFS filesystem.

I would like to know if there are any solutions to the problem I'm currently facing. Is it a bug related to OS X or something wrong on my end?

Any help would be greatly appreciated.

Thanks.

MacBook Pro with Retina display, OS X El Capitan (10.11.2)

Posted on Dec 27, 2015 3:03 AM

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Answer 1

Dec 27, 2015 12:27 PM in response to avanissh

Although I haven't run into it myself, it's been reported that the FAT and exFAT formatting done by Disk Utility on Flash drives can have compatibility problems on Windows PC's. Since Flash drives typically come formatted for Windows, the best advice is leave their formatting alone and just use them. 32GB Flash drives are going for $11 so I'd suggest buying one, copying what's on the problematic drive to that, and using it instead for both the Mac and Windows.

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Answer 2

avanissh Author

Level 1

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Dec 27, 2015 6:48 PM in response to FatMac-MacPro

That is not the only issue though. Thought I mentioned it in the original post.

Thing is, a USB formatted using Windows.. once I use it on my mac no longer works on WIndows again. It asks to be formatted again. And buying a new one is not a solution I am looking for sadly. It would have been fine if I was working with 1 USB or 1 external HDD. 😟

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Answer 3

steve359

Level 6

17,181 points

Dec 27, 2015 11:26 PM in response to avanissh

Technical reason for the Windows/Mac issue with ExFAT ... Mac uses a fixed/unchangable setting for blocksize. This blocksize does not work for Windows. But Windows uses a blocksize to format that Mac can live with.

I have a Windows-formatted-ExFAT USB that I have regularly used on both and the Windows has not found it "unusable". I am not suggesting you are doing anything wrong, just saying I have no solution because I do not have that particular problem.

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Answer 4

Courcoul

Level 6

18,588 points

Dec 28, 2015 12:33 AM in response to avanissh

Which Windows did you use? Win8 came out much more finicky as to the specific details of the ExFat format it would use and/or accept so it became mandatory to format any mixed-use stick on that system instead of the Mac. I would suppose that Win10 would be a continuation of the same, but I've tried to remain as distant as possible from the thing. Win7 and predecessors had no issue with the Mac's interpretation of the Fat or ExFat format specs.

Also, rereading your first post, have you made certain to eject the device prior to unplugging EVERY time? This kind of behavior I've seen when the stick was yanked summarily from either Mac or PC before the system had a chance to consolidate all changes made to it (which occurs by ejecting and/or waiting a sufficient time for the system to put the device in a semi-dormant state).

In any case, it seems that you will have to salvage what you can in whichever system manages to recognize its contents and reformat (with the above recommendations in mind). Pretty sure the damage is logical and not physical (unless the stick is truly ancient).

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