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Data Integrity

By: uCertify Posted on: 2006-07-11 Downloads: 204

Article Summary: Compression is a technique through which the actual size of a file stored on a hard disk can be reduced. It reduces the overall number of bits and bytes in a file so that the compressed file can be transmitted faster over slower Internet connections and occupies very less space in storage devices.

Compression of files, folders, and programs can be performed in Windows XP Professional by two ways: NTFS compression and Compressed (zipped) Folder.

Note: Since Windows 2000 supports compression only on NTFS volumes, but compressed NTFS files moved or copied to a FAT volume are automatically decompressed. Similarly, compressed NTFS files copied or moved to a floppy disk are automatically decompressed.

NTFS compressed Files and Folders: NTFS is a preferred file system on Windows NT family, including Windows XP, Windows 2000, Windows 2003, and Windows NT. Compression is available on a volume that uses NTFS file system. NTFS supports compression on volumes, folders, and files. Files that are compressed on an NTFS volume can be read and written by any Windows-based application without first being decompressed by another program. Decompression takes place automatically at the time the file is being read. The file gets compressed again, when it is closed or saved.

Each file record on NTFS volume is represented by a specific file called Master File Table (MFT). First 16 records are reserved for special information. Each record belongs to some file. More over, the file system metadata (information that describes the file system itself) is part of a file.

The first record is the master file table description, and the second record is identical to MFT record. If the first record corrupted, NTFS finds all record safe from the MFT mirror file. The location for both the MFT and the MFT mirror file are recorded in boot sector. So the NTFS file system has powerful security feature rather than FTP file system. Compression reduces the overall number of bits and bytes in a file so that it can be transmitted faster over slower Internet connections.

NTFS compression: Any file or folder in the individual order can be stored on a disk in the compressed form. Files that are compressed on an NTFS volume can be read and written by any Windows-based application without first being decompressed by another program.. The file compression has very high speed. You can set properties for your compressed files and folders. These happen separately in files, subfolders, and folders. You must have appropriate permissions to change the compression setting of files and folders. Uncompressed folders can have compressed files or vice versa. NTFS compression is based on Lossless compression algorithm that is Lempel-Ziv compression. No data is lost in file compression and decompression.

• NTFS file compression is performed without requiring changes to existing applications.
• We can use different colors to identify the NTFS compressed files and folders.
• NTFS compression is used individually to compress files, subfolders, and folders and compress a folder without compressing its files.
• You can use compressed file without changing it back into its original (decompressed) form.
• You may encounter a problem when you work with NTFS compressed files. For instance, when you open a compressed file, you find it decompressed, or when you compress a file and close it, Windows automatically decompresses it.
• Uncompressed folders may have compressed files and compressed folders may have uncompressed files.
• Windows determines the color of compressed files and folders to distinguish them from those uncompressed.

Note: NTFS compressed files and folders cannot be encrypted.

Copying and Moving NTFS Compressed Files and Folders

When a user copies or moves files or folders from one folder to another within a single NTFS volume, between the NTFS volumes, or between the NTFS and FAT volumes, the original permissions assigned to the files or folders may not necessarily change. There are several specific rules that govern how and when the permissions change. These rules are as follows:

• When a user copies a file or a folder within a single NTFS volume or between NTFS volumes, the original configuration of the file or folder changes, and it the file or folder inherits the permissions assigned to the destination folder.
• When a user copies or moves a file or a folder from the NTFS volume to the FAT volume, all the original permissions assigned to the file or folder are lost.
• When files and folders move between a single NTFS volume, theythe files and folders keep the original permissions assigned.

When files and folders move between NTFS volumes, the original permissions assigned to them changed and the they inherit the permissions of the destination folder. The destination folder must have write permission to include moving files, folders, and its contents in it.When a user copies a files or a folders with in a single NTFS volume or between NTFS volumes, Windows XP treats it as a new file or folder. Hence, a user must have write permission on the s or folders where he wants to copy the files or folders. When a user moves or copies the files or folders from NTFS volumes to FAT volumes, all the NTFS permissions assigned to them are lost because FAT volumes do not support NTFS permissions. If files are copied to a NTFS volume, NTFS allots uncompressed file size spaces on the hard disk, but if there is not enough space for uncompressed file too, the file can not be copied.

NOTE: Basically, everything on the volume is a file, and everything in a file is an attribute, the data attribute, the security attribute, and the file name attribute. And an attribute is identified by its type, code, and name.

Assigning File Permission

To control accessing permissions, are granted to users, groups, and application of files, on folders and files. In this way 5 NTFS file permissions are assigned to files and folders to control the accessing.:

1. Read
2. Write
3. Read & Execute
4. Modify
5. Full Control

"By default, folder permissions supersede file permissions. For example, if a file has Deny Access permission and a user has Full Control permission on the folder, in where the file resides, he will be able to delete the file"
If a user has been granted modify permission on files or folders, he is allowed to read, write, and execute the files or folders. Hence, there is no need to assign multiple permissions. The NTFS folder permission allows users and groups to access files, folders, and subfolders. The NTFS folder permission is to secure any particular folder or file and confine the users' accessibility.

When you run the Planning NTFS Permissions file, the full control permissions are granted to users and groups. The NTFS folder permission allots the access permissions to folder, files in that folder, and contained subfolders of that folder.

Following are the types of access that NTFS permissions to help you organize the data and manage the resources on a network:

NTFS permission	Folder	File
Read	View files and subfolders, folder ownership, permission and attribute.	Read the file and view ownership, permission and attribute.
Read	View files and subfolders, folder ownership, permission and attribute.	Read the file and view ownership, permission and attribute.
Write	Create new folder and files, change folder attribute, permission and ownership.	Change ownership, permission and attribute of files.
Write	Create new folder and files, change folder attribute, permission and ownership.	Change ownership, permission and attribute of files.
Modify	Delete folder and do all the actions permitted by Read & Execute and write permission.	Modify and delete the folder and performed all action permitted by write and Read & Execute permission.
Read & Execute	Navigate through all files and folder and performed all action permitted by read permission.	Run applications and performed all action permitted by read permission.
Full Control	Change permissions, take ownership, delete subfolders and files, and perform actions permitted by all other NTFS folder permissions.	Change permissions and take ownership, and perform the actions permitted by all other NTFS file permissions.td>

Note:List Folder content permission is separately allotted to a folder to list all the named files and subfolders in it.

Article Source: http://www.upublish.info

About the Author:
uCertify

About the Author:

uCertify was formed in 1996 with an aim to offer high quality educational training software and services in the field of information technology to its customers. uCertify provides exam preparation solutions for the certification exams of Microsoft, CIW, CompTIA, Oracle, Sun and other leading IT vendors. To know more about uCertify, please visit http://www.ucertify.com/