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Notes on NTFS
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TreeSize Professional is able to compress and decompress entire file system branches using
the context menu.
The NTFS version that comes with Windows 2000 supports an additional concept that is similar
to compressed files: sparse files. Files which are large but only partially used are called sparse
files. Because the operating system does not allocate disk space for the unused parts of a
sparse file, it occupies less disk space than its actual size is. TreeSize Professional treats
sparse files like compressed files and also calculates the compression ratio for them.
Reparse Points: Volume Mount Points and Symbolic Links
Since Windows 2000 NTFS supports volume mount points and symbolic links. A volume mount
point is an existing path where you "mount" another volume. Given this, users and applications
can refer to the mounted volume by that path. It allows you to unify disparate file systems into
one logical file system. Symbolic links work similar: If you for example have an empty folder "C:
\Documents\Images", you can create a symbolic link to "E:\Pics" in it. Applications will then see
the content of "E:\Pics" in "C:\Documents\Images".
If the Option "Follow Mount Points and Symbolic Links" is turned on, TreeSize Professional will
include the contents of these folders when scanning. Since they are not physically stored on the
drive you are scanning, this may produce irritating results.
Alternate Data Streams (ADS)
In NTFS, a file consists of different data streams. One stream holds the security information
(access rights and such things), another one holds the "real data" you expect to be in a file.
There may be alternate data streams, holding data the same way the standard data stream
does. These alternate data streams are hidden. That means that you can have a file with 1 byte
in the official main data stream and some hundred MB in one or more alternate data streams.
The dir command, file managers or windows explorer will show 1 byte as the size of this file, but
it actually allocates more space on your hard drive.
TreeSize Professional can detect alternate data streams and add their sizes to the allocated file
size.
Note: ADS stores information in the same cluster as the main data stream, so if a file has one or
more ADS, this file does not necessarily allocate more disk space.
You can choose to detect alternate data streams, to get a more accurate allocated space of
directory branches, in the Options Dialog.You can search for Files containing alternate data
streams using the Custom File Search of TreeSize Professional.
Hard Links
In a Windows environment a hard link is a reference, or pointer, to physical data on a NTFS
storage volume. All named files are hard links. The name associated with the file is simply a
label that refers the operating system to the actual data. On NTFS volumes more than one
name can be associated with the same data. Though called by different names, any changes
made will affect the actual data, regardless of how the file is called at a later time. Hard links can
only refer to data that exists on the same file system. The data is accessible as long as at least
one link that points to it exists. When the last link is removed, the space is considered free.
If more than one hard link points to a file's data, the space allocated by these files is just one
time the file size (not including the space of the file master table), no matter how many hard links
exists TreeSize Professional is able to detect the number of hard links pointing to one file data
TreeSize Professional - Notes on NTFS