(why) is FSCTL_SET_OBJECT_ID dangerous?

Question

NTFS files can have object ids. These ids can be set using FSCTL_SET_OBJECT_ID. However, the msdn article says:

Modifying an object identifier can result in the loss of data from portions of a file, up to and including entire volumes of data.

But it doesn't go into any more detail. How can this result in loss of data? Is it talking about potential object id collisions in the file system, and does NTFS rely on them in some way?

Side node: I did some experimenting with this before I found that paragraph, and set the object id's of some newly created files, here's hoping that my file system's still intact.

Answer 1

I really don't think this can directly result in loss of data.

The only way I can imagine it being possible is if e.g. a backup program assumes that (1) every file has an Object Id, and (2) that the program is keeping track of all IDs at all times. In that case it might assume that an ID that is not in its database must refer to a file that should not exist, and it might delete the file.

Yeah, I know it sounds ridiculous, but that's the only way I can think of in which this might happen. I don't think you can lose data just by changing IDs.