I back up my data on NTFS Windows formatted external hard drives (different brand names), cloning each drive to protect against hardware failure. I copy from Mac, Windows, Linux, or Android machines onto one HDD and then make a clone of the HDD with my Mac OS X. I buy the HDDs in pair so they are also physically the same.

I was not aware of the challenges of copying to Windows NTFS HDDs with Mac OS X, and copy-pasted across HDDs without special care. I have had the XtraFinder app installed and apparently it allows me to copy onto NTFS without warning or error messages.

But there are problems with some of the copied files (The problems have nothing to do with a size limitation, as this can happen with files of just a few MBs).

Example of problems: I have 2 identical hard drives straight out of the box (brand new WD Ultra Passport, not faulty), HD1 and HD2. First, I copy a video from my Windows computer onto HD1. Secondly, I copy the same video from HD1 to HD2 using the Finder on Mac OS X. Result: The video can be played off HD1 but not off HD2. Whether I try to play the video on the Mac or a Windows or Android machine, same result. So the video copied from HD1 to HD2 appears to be seriously corrupted.

The corruption is a little subtle because FreeFileSync does not detect differences between the files on the HDDs. It's only when I try to play the video from the cloned HDD that I get an error message.

  1. Is there a way to detect the corrupted files?

  2. Is there a fix for the corrupted files?

I have tested this with mkv and mp4 video formats and standard image formats (photos taken with my cameras or phones). Some videos are copied without trouble, other videos are broken after being copied. With images, problems tend to affect a random number of them rather than all of them, maybe 1 in 20 or so. There are no problems at all if I copy with my Windows machines.

This problem has occurred with a dozen or so hard drives. They are formatted as "Windows NT Filesystem" (as read from "Get Info" menu) The problem has occured with previous versions of the OS (Mavericks and Mountain Lion). I have usually backed up with FreeFileSync, to copy large number of files at a time, and the problem has occurred that way too, not just copy-paste via the Finder.

MacBook Air, OS X Yosemite (10.10.3)

P.S. I have asked the question on apple discussions, but have not received answers at the time of posting here.

  • 1
    Can you add these details to your question - comments are ephemeral & can be deleted at any time. Also add what you are using to enable write to NTFS on the Mac. – Tetsujin May 18 '15 at 6:52
  • Not sure if this is useful info: If I cut and paste a file (or several files) "too quickly" from one directory to another of my external hard drive, I occasionally get an error message and the file disappears. I can retrieve it by running a Disk error check on my Windows machine. Strange. I have learned to wait 2 seconds after doing "cut" and before "paste", and the problem disappears. – PatrickT May 18 '15 at 6:53
  • You can't 'cut' in the Finder. – Tetsujin May 18 '15 at 6:55
  • @ Tetsujin, can you clarify? By cut-paste I mean that I use command+X and command+V combinations. No apparent problems with, say, PDFs. Under the Edit menu of the Finder, there is a Cut command. – PatrickT May 18 '15 at 6:57
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    It works in apps, but you cannot Cut a file in Finder. Pick any file, look at the Edit menu, Cut is greyed out. Cmd/x ought to just beep. – Tetsujin May 18 '15 at 6:59

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