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File systems under Windows


File System.

In computer term, a file system is a way of managing and storing data files in order to find them and easily access. File system (disk file system) provides the following functions:

Efficiently use the space on the hard drive to store the data.
Catalog all the files for fast retrieval.
Support performance of basic file operations, such as delete, rename, copy, and move.
Provide some kind of data structure that allows a computer to boot off the file system.
Provide additional functionality, such as compression, encryption, and password.

Most file systems are integrated into operating system. Windows operating system uses FAT( File Alocation Table) and NTFS (New Technology File System) .

Disk Configuration.

In order the operating system enables to allocate information to disk, space on a hard drive is divided into sectors of 512 bytes each. Operating system grouped these sectors into clusters. All clusters normally run from 2 to 64 sectors. Each file usually reserves one or more of these clusters. The cluster size depends on the operating system and some factors, such as a size of hard disk and its partitions. There are some other different areas located on the disk for necessary system operations. That is an area for boot processes and an area for information of program files properties and physical location. When the computer procedure requires a specific file, these file properties allow the system to find and load that file from disk into RAM (Random Access Memory) for processing. FAT and NTFS have completely different approaches in that procedure. Let's outline some of the characteristics of two different file systems.

FAT32.

FAT was named for the type of database called a File Allocation Table that contains the entries for each file on the disk. Each record inside the FAT takes 32 bytes of space:

Byte Range Info Stored
1 to 8 Filename
9 to 11 Extension
12 Attributes (read-only, archive, hidden)
13 to22 Reserved bits for latter features
23 to 24 Time written
25 to 26 Starting cluster
29 to 32 File size

Every record in the FAT uses 4 bytes to store the size of the file. It actually tells that the maximum size possible for any single file is 4 bytes or 32 bits, which is a number with 32 digits. The number refers to the number of bits used for the cluster number in the table. And since it can handle a bigger number of clusters, its cluster size is much smaller than that of FAT16 for bigger disks. In fact, FAT32's maximum disk size is 2 Terabytes. FAT32 provides a larger number of clusters per partition (for all hard disks under 8GB) and improves the disk space efficiency by decreasing the cluster size as small as 4K and reducing the amount of unused space. For example, on a 1GB hard disk using the old FAT system, a 1KB file takes up 32KB of space. However, a 1KB file on the same hard disk using the FAT32 system takes up only 4KB of space, a savings of 28KB. When dealing with an entire hard disk that has thousands of files, the savings is remarkable.
FAT32 has improved reliability over its previous versions replacing the root directory from the beginning of the hard disk as it was before. Under the FAT32 system, the root folder can be relocated anywhere on the hard disk, and the backup copy of the file allocation table can be used instead of the default copy. Both FAT32 and FAT16 store two copies of the file allocation table on disk. But FAT16 can only read from one of them while in FAT32, the system could choose to read from either one, which provides a better fail-safe.
The extended boot record on FAT32 drives includes a backup copy of critical data structures, so FAT32 drives are less vulnerable to any kind of failure involving corrupt file tables. FAT32 support the root directory unlimited in size. That means that you can have as many files and directories as you'd like. In FAT16, you could have a maximum of 255 directory entries.
Windows 95 OSR2, Windows 98, and Windows Me include an updated version of the FAT32 file system. This file system can also be installed on the Windows 2000-server and professional version, Windows XP and Windows 2003, even if they support NTFS file system.

NTFS.

While FAT32 was a decent system, there is a lack of some of the most advanced features that many businesses need to run on a network. Crucial are file level security, encryption, event logging, error recovery and compression. The NTFS file system provides file-level security, file-by-file compression, quotas, auditing and encryption. It also supports large volumes and powerful storage solution such as RAID.
In NTFS, everything that has anything to do with a file (file name, creation date, access permissions and contents) is stored as metadata or metafiles(collection of data including multiple content items). In NTFS, the file name, its data, and its attributes have equal rights.Since files are used, the system areas can be modified, enlarged, or moved as is needed. An example of one of the several system files is the Master File Table (MFT). The MFT is a specialized database storing information about all files on the disk, including name, attributes, and location on the disk. Each attribute can be encrypted and compressed. Directories are also special files, containing list of files and subdirectories within them. If a file is small (1 KB or less) the MFT may even hold the file itself. For larger files NTFS uses clusters in assigning disk space but in a way different from FAT. Clusters on an NTFS volume are numbered sequentially from the beginning of the partition into logical cluster numbers. Because NTFS uses different cluster sizes depending on the size of the volume, each file system has a maximum number of clusters it can support. The smaller the cluster size, the more efficiently a disk potentially stores information because unused space within a cluster cannot be used by other files. The cluster size will not normally exceed 4 KB. A type of individual file compression is built in so that the problems with slack do not arise. This design makes file access very fast. NTFS, unlike FAT file system, which uses a file allocation table to list the names and addresses of each file and then retrieves the file by searching the chain of allocation units assigned to the file, looks up the file, and it's there for you to use.
The following table describes each of the organizational structures on the NTFS volume.

Components Description
NTFS Boot Sector Contains the BIOS parameter block that stores information about the layout of the volume and the file system structures, as well as the boot code that loads Windows Server 2003.
Master File Table Contains the information necessary to retrieve files from the NTFS partition, such as the attributes of a file.
File System Data Stores data that is not contained within the Master File Table.
Master File Table Copy Includes copies of the records essential for the recovery of the file system if there is a problem with the original copy.

-The most important NTFS features.

Large file/volume sizes (up to 2 terabytes).
Built in compression.
Built in encryption.
Automatic recovery.
Fine grained Access Control and auditing support.
Less slack space.
Multiple Named Streams.
Hard-Links.
Reparse Points (Soft links, Junction points, Volume Mount Points, DFS, etc.).
Quota support.
Extended attributes.
Multiple file namespaces.
Directories are stored in a balanced tree.
Sparse files.

NTFS is installed into Windows NT, including its later versions Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, and Windows Vista.

General differences between FAT and NTFS:

File System NTFS FAT32
Operating System Windows NT Windows 2000 Windows XP Windows 2003 Server DOS Windows 98 Windows ME Windows 2000 Windows XP
Volume Size Up to 2TB Up to 2TB
Files on Volume Unlimited 4194309
File Size Limited by Volume Size 4GB
Number of clusters Unlimited 4177918
Boot Sector Location First and Last Sectors First Sector and Sector #6
File Attributes Standard and Custom Standard
Alternate Streams Yes No
Compression Yes No
Encryption Yes No
Object Permissions Yes No
Disk Quotas Yes No
Sparse Files Yes No
Reparse Points Yes No
Volume Mount Points Yes No
Built-In Security Yes No
Recoverability Yes No
Fault Tolerance Maximum Minimum
Disk Space Economy Maximum Average


WinFS to replace FAT and NTFS.

The current situation, when new hard drives get bigger and faster, and people enable to store millions of files and organize their personal data (e-mail, documents, pictures, and digital music), requires a new-generation file system, which will be able to provide advanced data organization and management capabilities. The present file systems support folders and files well when the number of files is relatively small. However, we have a problem today in that we have lots of stuff to store and no good way to categorize it. Another problem is that we store the same stuff in multiple places and in multiple formats. For example, Microsoft Outlook and Microsoft Windows Address Book have its own definition of a Contact. Therefore, each application stores its definition of a contact in a unique format. Current file systems cannot share common data, and user repeatedly enters the same information. WinFS (Windows Future Storage) being developed by Microsoft for use on its future Windows Operating System will help users organize their data and allow applications to categorize information in multiple ways and relate one item of information to another. It provides a common storage format for information collected on an everyday basis, such as information dealing with People, Places, Images, Documents, and more. WinFS users will be able to build queries that use such relationships. Also, it promotes data sharing of common information across multiple applications.

There are five ways to organize information in WinFS:

1. Hierarchical folder-based organization. You still have the traditional hierarchical folder and file organization structure.
2. Type-based organization. You can organize all data in a particular type, for example, Person items, Photo items, Organization items, and many other available types. You can even create new types and store them in the WinFS data store.
3. Item property-based organization. You can view items that have one or more properties set to specified values.
4. Relationship-based organization. You can get items based on their relationship to other items-for example, a Person can be a member of a Group.
5. Category-based organization. You can create and relate any number of user-defined keywords with an item.

The WinFS data store provides a far richer data storage model than traditional file systems, because it supports data, behavior, and relations. It's difficult to categorize WinFS as a file system, a relational database, or an object database. It's a complex of all those technologies in one product.