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I'm trying to transfer a 60GB folder from a Time Machine backup of a dead MBP to my 128GB USB-C flash drive (ExFAT). Unfortunately, whenever the transfer is almost complete, an alert informs me that my flash drive is 'full' and then truncates the transfer. This is weird, because my flash drive is newly formatted (no .trashes), and the size of the folder to be transferred is clearly much smaller than the maximum capacity of the flash drive. The folder ends up being only partially transferred. Furthermore, I start having trouble mounting the flash drive after the truncated transfer; the drive only mounts after I kill fsck.

All of the sub-folders of my 60GB folder can be transferred out individually – quickly and without any problems – except for one folder (projects). This folder contains ~400,000 items, primarily in node_modules folders. I believe that the large number of items might be causing the transfer to fail, but I can't figure out why.


My questions:

  1. What am I doing wrong and how should I go about transferring my folders?
  2. Why does my newly formatted 128GB flash drive show that it is full when it only contains a 60GB folder? Does this have anything to do with the large number of files?
  • First test would be to run the Fight Flash Fraud app F3X & make sure the drive is the size it claims to be. – Tetsujin Dec 17 '18 at 11:09
  • @Tetsujin I ran f3write and f3read on the volume and it returned Data OK: 115.67 GB (242583841 sectors) Data LOST: 0.00 Byte (0 sectors). Seems to show that my drive is legit but thanks for the tip! – sabriele Dec 17 '18 at 17:20
  • OK, next thought - Time Machine uses aliases/symlinks everywhere - are you sure it's not trying to find & copy the 'original' of every symlink? tbh, how to avoid it is above my pay-grade ;) I just know it can happen. – Tetsujin Dec 17 '18 at 17:23
  • @Tetsujin "above my pay-grade ;)" hahahah. Re: "aliases/symlinks everywhere" I actually am not too sure.. If there was a way of copying the files and folders out without that I'm more than happy to accept that as an answer! – sabriele Dec 17 '18 at 17:26
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Time Machine uses hard links to link to multiple copies of the exact same data. Hard links are one of many features that exFAT does not support.

If you were to copy multiple files that link to the same data to an exFAT drive, it would be duplicated for each hard link, potentially making the resulting copy much larger than the original.

To avoid these problems, you should probably only ever copy Time Machine backups to an HFS+ or APFS drive. If reformatting the external drive is not an option, you might consider creating a disk image of the backup directory and save it to the external drive (via Disk Utility or the command line).

  • Thank you for the explanation as well as a solution, I really appreciate it! – sabriele Dec 19 '18 at 10:46

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