CHANGE THE DRIVE LETTER FOR A VOLUME

10-29Lesson 2 Managing Compression

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Figure 10-13

Compressed folders are labeled with a zipper icon.

How to Compress Files, Folders, or Volumes by Using NTFS

Compression

Unlike compressed folders, NTFS compression is a function of the NTFS file system

and as such is available only on volumes formatted with NTFS. Files compressed with

NTFS compression can be read and written to by any Windows-based or MS-DOS–

based application without first being uncompressed by another program. When an

application or an operating system command requests access to a compressed file,

NTFS automatically uncompresses the file before making it available. When you close

or explicitly save a file, NTFS compresses it again.

Note NTFS allocates disk space based on uncompressed file size. If you copy a com-

pressed file to an NTFS volume with enough space for the compressed file, but not enough

space for the uncompressed file, you might get an error message stating that there is not

enough disk space for the file, and the file will not be copied to the volume.

How to Compress a Folder or File

You will use Windows Explorer to set the compression state of folders and files. To set

the compression state of a folder or file, right-click the folder or file in Windows

Explorer, click Properties, and then click Advanced. In the Advanced Attributes dialog

box, shown in Figure 10-14, select the Compress Contents To Save Disk Space check

box. Click OK, and then click Apply in the Properties dialog box.

Note NTFS encryption and compression are mutually exclusive. For that reason, if you select

the Encrypt Contents To Secure Data check box, you cannot compress the folder or file.

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Figure 10-14

Use the Advanced Attributes dialog box to compress a file or folder.

Important To change the compression state for a file or folder, you must have Write per-

mission for that file or folder.

The compression state for a folder does not reflect the compression state of the files

and subfolders in that folder. A folder can be compressed, yet all the files in that folder

can be uncompressed. Alternatively, an uncompressed folder can contain compressed

files. When you compress a folder that contains one or more files, folders, or both,

Windows XP Professional displays the Confirm Attribute Changes dialog box, shown in

Figure 10-15.

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Figure 10-15

Use the Confirm Attribute Changes dialog box to control what happens to files and

subfolders inside a folder you are compressing.