Understanding Disk File Systems

A disk must be formatted with a file system that allows it to work with the operating system to store, manage, and access data. Two of the most common file systems are FAT (or FAT32, which is an improvement on FAT technology) and NTFS. Disks on DOS, Windows 3.1, or Windows 98/Me computers use the FAT file system, while disks on computers running Windows NT 4.0, Windows 2000, Windows XP and later can use either the NTFS or FAT system. NTFS is a newer file system that improves on some of the shortcomings of FAT disks that make them less desirable on a network. Which file system your disks are most likely to use and why depends on the type of disk, whether your computer is on a network, and your computer's role as a resource on the network.

There are important differences between FAT and NTFS file systems:

FAT

When you format a disk with the FAT file system, a formatting program divides the disk into storage compartments. First it creates a series of rings, called tracks , around the circumference of the disk. Then it divides the tracks into equal parts , like pieces of a pie, to form sectors. The number of sectors and tracks depends on the size of the disk.

Although the physical surface of a disk is made of tracks and sectors, a file is stored in clusters. A cluster, also called an allocation unit , is one or more sectors of storage space. It represents the minimum amount of space that an operating system reserves when saving the contents of a file to a disk. Thus, a file might be stored in more than one cluster. Each cluster is identified by a unique number. The first two clusters are reserved by the operating system. The operating system maintains a file allocation table (or FAT) on each disk that lists the clusters on the disk and records the status of each cluster, whether it is occupied (and by which file), available, or defective. Each cluster in a file "remembers" its order in the chain of clusters ”and each cluster points to the next one until the last cluster, which marks the end of the file. The FAT and FAT32 formats provide compatibility with other operating systems on your computer, which means you can configure your computer for a dual-boot or multi-boot setup and you can backup a previous operating system.

NTFS

NTFS features a built-in security system that does not allow users to access the disk unless they have a user account and password with the necessary rights and permissions. NTFS protects disks from damage by automatically redirecting data from a bad sector to a good sector without requiring you to run a disk-checking utility. Given the reliability and the built-in repair mechanisms of NTFS disks, only rarely do they require maintenance. This is an example of fault tolerance , the ability of a disk to resist damage, which is a critical issue with disks on a network computer.

Selecting a file system

NTFS does not support floppy disks, so all floppies are formatted with FAT. If you are running Windows XP on a stand-alone computer, you can choose either FAT or NTFS, but in most cases, the file system has already been determined either by the person who originally set up the computer or by the manufacturer from whom you purchased the computer. If your computer is a client on a Windows XP network, it is likely that your hard disk uses NTFS. Because NTFS is more suited to network demands, such as a high level of security and resistance to system failure, network administrators format network disks with NTFS whenever possible. Sometimes, however, users on a network want or need to use a non-Windows XP operating system. Also, a user might need a computer that is capable of running Windows XP or Windows 98/Me. The disks on that computer would then be formatted with FAT.

User Interface Differences

Feature

FAT

NTFS

Security

Vulnerable to "hackers" ”unauthorized users who break into other people's files

Includes built-in security measures that allow only people who have permission to access files

Recoverability

Likely to fail if a sector containing system data is lost because it stores critical system files in single sectors

Highly reliable because it uses redundant storage ”it stores everything in vital sectors twice, so if a disk error in a vital sector occurs, NTFS can access file system data from the redundant sector

File size

Designed for small disks (originally less than 1 MB in size); can handle a maximum file size of 4 GB

Handles files up to 64 GB in size




Show Me Microsoft Windows XP
Show Me Microsoft Windows XP (2nd Edition)
ISBN: 0789733366
EAN: 2147483647
Year: 2002
Pages: 391

flylib.com © 2008-2017.
If you may any questions please contact us: flylib@qtcs.net