Hello there, today we're going to talk about NTFS(or New Technology File System)'s compression method. This file system was implemented since the introduction of Windows NT, in July 1993, as an added security as the file system uses an unique file system table and thus able to allow encryption and compression of files. It has severeal improvements over FAT(File Allocation Table used by DOS to Windows ME) and HPFS(High Performance File System). Till this day, no other 3rd party software or applications is able to fully ultilize the NTFS file system.

The file system has gone through 4 major changes, so now it have a total of 5 versions. The latest is version 3.1, which is used in Windows XP, Windows Server 2003 and Windows Vista. Thanks for the unique table of NTFS, only volumes with more than approximately 4 GB of diskspace can be formatted with NTFS.

In NTFS, it supported two main features, the compression and encryption of files. But in this article, we will only understand about how the compression feature work about.

NTFS Compression feature really is a great function as you are able to free quite a large amount of disk space especially when you have quite alot of files on an NTFS formatted volume and requires a little more physical disk space. If you compressed a file and you take a look at its properties, you'll notice that there are two file sizes listed there. The "Size" property would show that how much byte does the file really contain. Whereas the "Size on disk" property would show the value of how many clusters the file take up multiplied by the size of each cluster(eg 512 byte).

Understanding a little more about the compression, the file system compresses a particular file when the operating system releases the file handle on the file and uncompresses when the operating system open the file. Therefore, it might take sometime to open up a very large file, and this becomes even more significant when you use a very large disk.

Also, even if you copy a file from an NTFS compression enabled folder to another NTFS compression enabled folder, be it the same folder or different disk, the file system would just simply uncompress, copy the file, then compress again. This decreases the overall performance of your computer.

If you noticed, sometimes if you compressed your WHOLE volume, and you try to boot, the screen will display something like "BOOTMGR is compressed. Press Ctrl+Alt+Del to restart". This is due to compression by the NTFS, because the driver for NTFS is not loaded yet, you cannot uncompress the file before the driver is loaded. Therefore you cannot boot from the BOOTMGR file. This applies also to NT systems where it says "NTLDR" instead of Vista's "BOOTMGR".

To conclude this, try not to compress your whole disk, especially your system disk. Frequent access to the files would cause performance disintegration. When do we compress files? Compress your seldomly used, small, old files. This would help in gaining disk space. Also, compressing your pagefile is the worse scenario ever.

Well, i hope that this article would help you understand NTFS file system better.

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