What is NTFS?

NTFS stands for NT File System, where NT refers to Microsoft Windows NT and means "New Technologies". Currently it is the best file system available for Microsoft Windows operating systems.

Understanding a file system.

A file system is needed to organize and access information on a hard drive disk, optical media, diskettes and so on. Imagine that you have thousands files on your hard disk, but you don't have any index. What happens if you request a file? The system starts searching for it, but as the system has no clue on where the file may be located, it has to browse all the files from the very beginning. It would take minutes, in some cases even hours, to find a particular file.

Now, a typical operating system reads and writes dozens of files in one second. It is possible due to the fact that all the files are smartly organized.

But there is more to a file system than just indexing. Imagine that in our previous example (enriched with an index for quicker searching), you have opened a TXT file and added a few words to it. Now you press "Save". What happens?

The file is larger now than it was before opening. However, on your hard disk, there is no extra space reserved for it. The next file begins exactly where our file ends. No spare bytes. No space to save a few more words that we've added. What should we do?

One solution would be to reserve some extra space for every file... but how much? Some files are changed frequently, other files aren't changed at all, and we don't know any of that initially. How much space would be wasted with this approach?

Another solution would be to move our file into another location, where it is enough space for it. But as we delete the file from its former location, what should we do with the gap? Should we try to find another file that fits it, or should we simply dismiss it? How much space will be wasted if we systematically move files that become larger to new locations?

Yet another solution would be to save only a part of our file in its former location. The rest of it we save in some free area, and then we link the parts together.

The latter decision may seem to be smart and obvious, but it creates much more complexity than we'd like to bring up here. For one thing, the whole indexing should be changed. If we simply link one part of our file to the rest of it internally (inside the file), how the system should know that there is something in the free area? How should we prevent the system from writing another file into the same area?

All in all, modern file systems are quite complex, with lots of decisions and experience incorporated into the very design. What kind of decisions? Well, a file system should be: effective (as little as possible space should be wasted), fast, stable, secure, user-friendly (as an example, directories and long filenames should be supported) and so on. These are very different requirements, and they are often in conflict with each other: a fast system may want to skip significant areas of free space instead of writing multiple fragments, so it can't be effective; security slows a system down; stability requires to write some additional information, which takes both space and time. There are no ideal solutions, but there are solutions that are pretty good in most cases for the current level of technology.

NTFS is one of such solutions.

A brief history.

Some people nowadays consider Windows NT to be a long forgotten history, so the "New Technologies" stuff may seem to be funny. Yes, the first version of Windows NT was released back in 1993, what is so new about it?

However, Windows NT was a great step for Microsoft operating systems. While Windows 3.1 and Windows 95 were dragging the load of backward compatibility, NT introduced far better system design. This made it not compatible with earlier MS-DOS based operating systems, which was the reason why Windows 95 and Window 98 were much more popular (while the more secure and stable Windows NT existed for years!), but finally NT took over. Windows 2000, XP, Vista are built on basis of NT.

NTFS was one of those "new technologies".

MS-DOS, first versions of Windows, Windows 95, 98, ME - all of them used FAT, the predecessor of NTFS. First introduced in 1980, FAT (File Allocation Table) went through several revisions (among them are FAT12, FAT16, FAT32). It learnt to support folders, long filenames, large disks. However, the initial design contained several restrictions that finally made FAT outdated (well, not quite so: FAT is still used for smaller media, like diskettes).

NTFS dominates the world of Microsoft Windows operating systems since Windows 2000. Actually, all the following systems, including Windows XP, could be installed on FAT-formatted partitions, but restrictions of FAT made NTFS far more preferable.

Windows Vista demands an NTFS-partition for itself.

Versions of NTFS.

NTFS is still developed and improved. Basically, there are five versions:

  • v. 1.0
  • v. 1.1
  • v. 1.2 - Windows NT 3.51 and Windows NT 4
  • v. 3.0 - Windows 2000.
  • v. 3.1 - Windows XP, Windows Server 2003, Vista.

NTFS versions installed on the latest versions of Windows can also be referred to as NTFS 5.0, NTFS 5.1, NTFS 6.0. The number in this case matches the number of the operating system (Windows Vista is NT 6.0).

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