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NTFS System (Metadata) Files
As I mentioned in the architectural overview, the NTFS file system stores virtually all data, both user data and internal management data, in the form of files. The most important of these are a set of special system files, which are also called metadata files. The prefix "meta-" generally refers to something "transcendent" or "beyond"--or merely self-referring. So "metadata files" are files that contain data about data. And that's exactly what these files do. They contain internal information (data) about the "real" data stored on the NTFS volume.
These metadata files are created automatically by the system when an NTFS volume is formatted, and are placed at the beginning of the partition. Now, explaining how these files work is a bit complicated. :^) Understanding their location in an NTFS volume requires that I mention another key structure, the NTFS Master File Table (MFT). The MFT is actually one of these metadata files, but it also contains descriptions of the other metadata files, and in some cases entire other metadata files. Yes, it's a bit confusing. :^) Reading the page on the MFT will help you understand how it works, but in a nutshell, here's what happens: the MFT contains a record describing every file and directory in an NTFS volume, and if the file is small enough, its actual contents may be stored in the MFT itself. Since the metadata files are just "files" to NTFS (albeit special ones), they too have records in the MFT. In fact, the first 16 records of the MFT are reserved for metadata files.
Phew, sorry about that, but hey, I didn't design this thing. :^) Actually, the system is hard to explain, but it is logically consistent, and does work well. The table below provides the important information about the metadata files, including their English names, file names, MFT record numbers and a brief description of what each does:
Note: Records 11 through
15 in the MFT (the 12th through 16th records, since MFT records are numbered starting from
zero) are reserved for future metadata files.
The elegance of the metadata system is that by storing internal information in files, it is possible to expand on the capabilities of the file system--changing "dedicated" internal structures is more complicated. Also, these files do not need to be stored in a specific location on the hard disk, so if a specific area of the hard disk is damaged, they can be moved.
Next: Master File Table (MFT)