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I just received 4,000 4GB flash drives for my company. When we try to access video or PDF files that we've written to a folder the folder comes up empty.

For instance, on every drive we load a PDF and a folder with videos about our company. After copying over all the files, which says is successful, the folder is somehow empty. I don't see them with showing hidden files or through the command prompt or anything.

We have tried formatting them with exFat, NTFS and of course FAT32. We've tried to load the files on there manually on a computer or clone from a different flash drive on the duplicator. We've tried not putting the videos in a folder, but that didn't make a difference.

It seems that small files will sometimes stay but nothing very large will. Large files will disappear.

Windows 7

seizethecarp
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1 Answers1

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I tested the flash drive with a program called h2test2w.exe. The flash drive was mislabeled in the system as 4GB when it actually only had a 215MB capacity. I don't mean just mislabeled like what was printed on the outside -- I mean system properties, other drive analyzers, you name it.

Apparently the displayed size of the drive that every program uses is not based on the ACTUAL capacity of the chip, but on a bit of "header" information on the USB flash drive that someone manually sets with factory tools (see How do I make a USB partition so no one can erase it -- the last image in my answer there shows a Capacity Setting tab).

As long as we never put more than 215MB on the drive it acts fine, but any more than that and it seems to do a revolving overwrite of the first bits of the drive. Like this, if there were only 4 bits:

bit 1 value: 0
bit 2 value: 0
bit 3 value: 0
bit 4 value: 0

Now I will write a file with 6 bits to it: 000011

bit 1 value: 0 
bit 2 value: 0
bit 3 value: 0
bit 4 value: 0
bit 1 value: 1
bit 2 value: 1

Which leaves me with:

bit 1 value: 1
bit 2 value: 1
bit 3 value: 0
bit 4 value: 0

So if the "header" had been correct, it wouldn't have written to the drive since the drive was too small. Instead, now the first two bits have been overwritten and the file is corrupt or not even there.

In other words, we got scammed.

seizethecarp
  • 837