10-33Lesson 2 Managing Compression
BACopyMoveRetainsInheritsNTFS volume
CCopy Inherits
F10us17
Figure 10-17
Copying and moving compressed folders and files have different results.
Note When you copy a compressed NTFS file, Windows XP Professional uncompresses the
file, copies the file, and then compresses the file again as a new file. This might take consid-
erable time.
NTFS Compression Guidelines
The following list provides best practices for using compression on NTFS volumes:
■
Because some file types compress more than others, select file types to compress
based on the anticipated resulting file size. For example, because Windows bit-
map files contain more redundant data than application executable files, this file
type compresses to a smaller size. Bitmaps often compress to less than 50 percent
of the original file size, whereas application files rarely compress to less than 75
percent of the original size.
■
Do not store compressed files, such as PKZIP files, in a compressed folder. Win-
dows XP Professional will attempt to compress the file, wasting system time and
yielding no additional disk space.
■
Compress static data rather than data that changes frequently. Compressing and
uncompressing files incurs some system overhead. By choosing to compress files
that are infrequently accessed, you minimize the amount of system time dedicated
to compression and uncompression activities.
■
NTFS compression can cause performance degradation when you copy and move
files. When a compressed file is copied, it is uncompressed, copied, and then
compressed again as a new file. Compress data that is not copied or moved fre-
quently.
Practice: Managing Compression
In this practice, you use NTFS compression to compress files and folders. You uncom-
press a file and test the effects that copying and moving files have on compression. In
the last portion of the practice, you create a compressed folder using the Compressed
Folders feature.
Important In this practice, it is assumed that you installed Windows XP Professional on
the C drive, and that the C drive is formatted with NTFS. If you installed Windows XP Profes-
sional on a different partition and that partition is formatted with NTFS, use that drive letter
when the practice refers to drive C.
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