I’m trying to find out if there are any areas of a drive (preferably file-system–independent) which are never really used.

To clarify, I’ll demonstrate my use-case scenario. I am writing a tool to simplify and automate the inventorying of my removable media (I used to simply dir > …). I have numbered my flash-drives and memory-cards physically with a marker, and I would like to digitally number them as well so that the tool can use that number as an ID.

The problem is that putting the ID in a file or volume-label is not ideal for a few reasons:

  • It modifies the drive
  • It uses drive resources (space/directory entries/volume label/etc.)
  • It is conspicuous and too exposed (not that I want to hide it, but I don’t want it cluttering up the actual data)

I thought that one option might be to simply write to an unused part of the drive. Since the data would be really small (essentially just a single integer), it seems like there would be plenty of places to stash a little number in the vast unused areas at the start of a FAT* or even NTFS volume.

The concern of course is of the safety in doing this. Using undocumented or reserved functions and areas is always risky, but I’m hoping to find some sort of information (statistics, case-studies, etc.) which can indicate what is/are the safe-est area(s) to use. Naturally, this wouldn’t be a universal solution, because if multiple programs did this, then there could be a conflict, but certainly for personal use, it should be possible.


Almost all file systems already have unique IDs set at creation time (32-bit for FAT, 64-bit for NTFS, 128-bit for many Unix filesystems). It shouldn't be hard to make your inventory DB map filesystem UUID ↔ catalog ID.

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