MCSA/MCSE Self-Paced Training Kit (Exam 70-270): Installing ...

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NTFS volume
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Lesson 2 Managing Compression
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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 considerable
time.
NTFS Compression Guidelines
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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 bitmap
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. Windows
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 frequently.
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NTFS volume