What is the difference between a 64-bit fileid and a 128-bit fileid in Windows?

Jeremy Allison jra at samba.org
Tue Jul 7 21:39:54 UTC 2020

On Tue, Jul 07, 2020 at 01:32:05PM -0700, Richard Sharpe via samba-technical wrote:
> Hi folks,
> I have just become aware that Windows has both a 64-bit fileid and a
> 128-bit fileid.
> https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/2d3333fe-fc98-4a6f-98a2-4bb805aff407
> https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-fscc/98860416-1caf-4c80-a9ab-8d61e1ccf5a5
> Are they always equal if the fileid fits in 64 bits or are they different?

Hmmm. From these docs:

"NTFS computes the 64-bit file ID as follows: 48 bits are the index
of the file's primary record in the master file table (MFT), and the
other 16 bits are a sequence number. Therefore, it is possible that
a different file can have the same 64-bit file ID as a file on that
volume had in the past."

There is no info on how NTFS computes the 128-bit file ID.

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