File move - How does the OS know whether to update a master file table or copy and delete?

Question

After having read questions dealing with how to tell whether two files are on the same physical volume or not, and seeing that it's (almost) impossible (e.g. here), I'm wondering how the OS knows whether a file move operation should update a master file table (or its equivalent) or whether to copy and delete.

Does Windows delegate that to the drives somehow? _{(Or perhaps the OS does have information about every file, and it's just not accessible by programs? Unlikely.)}

Or - Does Windows know only about certain types of drives (and copies and deletes in other cases)? In which case we could also assume the same. Which means allowing a file move without using a background thread, for example. (Because it will be near instantaneous.)

I'm trying to better understand this subject. If I'm making some basic incorrect assumption - please, correcting that in itself would be an answer.

If needed to limit the scope, let's concentrate on Windows 7 and up, and NTFS and FAT drives.

Answer 1

Of course the operating system knows which drive (and which partition on that drive) contains any particular local file; otherwise, how could it read the data? (For remote files, the operating system doesn't know about the drives, but it does know which server to contact. Moves between different servers are implemented as copy-and-delete; moves on the same server are either copy-and-delete or are delegated to that server, depending on the protocol in use.)

This information is also available to applications. You can use the GetFileInformationByHandle() function to obtain the serial number of the volume containing a particular file.

Answer 2

The OS does have information about every file, and it's just not as easily accessible to your program. Not in any portable way, that is.

See it this way: Those files are owned by the system. The system allocates the space, manages the volume and indexes. It's not going to copy and delete the file if it ends up in the same physical volume, as it is more efficient to move the file. It will only copy and delete if it needs to.