Saturday, March 31, 2012

What is NTFS?

NTFS is the standard file system of Windows NT, Windows 2000, Windows XP, Windows Server 2003, Windows Server 2008, Windows Vista and Windows 7. NTFS replaces FAT file system and provides file system for operating system of Windows series of Microsoft. NTFS has improved FAT and HPFS (high performance file system) in several places. Fox example, it supports metadata and uses senior data structure to improve the property, reliability, and utilization ratio of disk space. It also provides several additional extended functions such as access control list (ACL) and file system journaling. The detailed definition of this file system is business secret, but Microsoft has registered it as an intellectual property product.

Overview of NTFS
NTFS (New Technology File System) is the file system of Windows NT operating environment and Windows NT advanced server network operating system environment.

Detailed Description
NTFS provides long file name, data protection and recovery, and implements security through directory and file. NTFS is in support of storing files (called volume) in large hard disk and multiple hard disks. For example, the data base of a company is so large that several hard disks must be used to store it. NTFS provides build-in security features which control file subordinate relationship and file access. Files on NTFS partitions can not be accessed in DOS or other operating systems directly. If users want to read and write NTFS partition files, the third-party software can be used. Nowadays, NTFS-3G is applied to read and write NTFS partition files perfectly without any data loss.

Win 2000 adopts newer edition of NTFS file system - NTFS5.0. Its release not only allows users to operate and manage computer as conveniently and efficiently as that in Win 9X, but also makes users to enjoy the system security brought by NTFS. The length of long file name permitted by NTFS is 256 bytes. Although DOS users can not access NTFS partitions, NTFS files can be copied to DOS partitions. Every NTFS file contains a DOS readable file name recognized by DOS file name format. And the name comes from the beginning character of long file name in NTFS.

Features of NTFS
Size of Partitions Supported

The size of partitions( it is called volume in dynamic disks ) that NTFS supports is 2TB at most while the size of partitions supported by FAT 32 in Win 2000 is 32 GB at most.

Reliable file system
NTFS is a presumable file system and users hardly need to operate the disk repair program. NTFS guarantees partitions consistency by using standard transaction log and recovery technology. When system failure occurs, NTFS will automatically recover consistency of system by using journal file and checkpoint information.

Support of Folder Compression
NTFS is in support of the compression of partitions, folders and files. Any application based on Windows can read and write compressed files in NTFS partitions without uncompressing by other program in advance. When reading and writing documents begins, files uncompress program will run automatically. And files will be compressed automatically when closed or saved.

Efficient Management of Disk Space
NTFS adopts smaller cluster to manage disk space efficiently. In FAT32 file system of Win 2000, when partitions vary from 2GB-8GB, one cluster is 4KB; when partitions vary from 8GB-16GB, one cluster is 8KB; and, when partitions vary from 16GB-32GB, one cluster is 16KB. However, in NTFS file system of Win2000, when the partition is less than 2GB, the size of cluster is smaller than that of FAT32. When the partition is bigger than 2GB (2 GB-2TB), every cluster is 4KB. Therefore, compared with FAT32, NTFS can manage disk space more efficiently and decrease disk space waste furthest.

Better Security
In NTFS partitions, users can set access permission authorities of sharing resources, folders and files. It contains tow aspects: one is which group or user can access the folders, files and sharing resources and the other is what level the group or user can access.

Set of access permission authorities is not only suitable for local computer users, but also suitable for network users who access files through network sharing folders. Compared with access to folders or files in FAT32 file system, it is more security in NTFS. In addition, in Win 2000 adopting NTFS format, audit policy can be used to audit folders, files and active directory object.

And audit results are recorded in security log. Through the security log, the administrator can check which group or user has accessed to folders files and active directory object and what level operation they have done. So the possible illegal access to the system can be found out and corresponding methods will be taken to reduce this kind of potential safety hazard furthest. And these can not be realized in FAT32 file system.

More Functions
NTFS file system can manage disk quota in Win 2000. Disk quota is that administrator can define the using space for users by quota limit and every user can only use disk space within the maximum quota. When disk quota is set, the disk usage of every user can be monitored and controlled. Through the monitor, the users exceeding quotas alarm threshold and quota limit can be identified and corresponding methods can be taken. The use of disk quota management makes the administrator allocate storage resources to users conveniently and reasonably. And this avoids system crash caused by disk usage space out of control, which increase the security of system.

NTFS also uses a "dynamic" log to record the change of files.
NTFS also contains encrypted file data and data related to system service and some other things

Advantages of NTFS
1. Having Error Warming File System
In NTFS partitions, the beginning 16 sectors are partition boot sectors, and it stores partition boot code. The following part is Master File Table (MFT). If the disk sector is destroyed, NTFS file system will intellectively transfer MFT to other sector of the disk, which makes the system used normally. That means Windows runs normally.

2. More Efficient in File Read
File attributes in NTFS can be divided into tow types: resident attributes and non attributes. Resident attributes are stored in MET directly. File name and related time information (such as creation time and modification time) belong to resident attributes forever. Nonresident attributes are not stored in MFT, but it can be indicated by a complicated indexed mode. If the files or folder s are less than 1500 bytes (there are many files or folders of this kind in a computer), all of their attributes and contents are resident in MFT. And MET will be loaded into RAM while Windows is started. Therefore, when the user look up the files or folders, they are in cache actually. And this increase the access speed of files and folders.

3. Self-Healing of Disk
NTFS adopts a "self-healing" system to monitor and amend the logical and physical error in disk.
During the time of FAT16 and FAT 32, Scandisk is needed to mark destroyed sector in disk. However, when the error is found, data have been written in the destroyed sectors, and the loss has been caused.

4. " Disaster Relief" Function of Event Logs
In NTFS file system, any operation can be considered as an "event". For example, the process of copying a file from Disk C to Disk D is an event. Event logs monitor the whole process. When the whole file is found in the target disk - Disk D, a sign of "finished" will be marked. If there is a power outage during the process, the event log will not mark "finished". NTFS can repeat the event when the power is on.

5. Dynamic Disk of NTFS
Dynamic disk is a new feature from the time of Windows 2000, and Windows 2003 continue to use this great feature. Compared with the basic disks, it provides more flexible management and operating characteristics. Operations such as data faults tolerance, high speed read and write operation, relative optional change of volume can be realized in the dynamic disk, but these operations can not be realized in basic disk. Dynamic disk has no limits to the number of volume. If disk space permits, users can create volumes without any limitations in the dynamic disk. No matter the dynamic adopts Master Boot Record (MBR), GUID partition table or GPT partition format, 2,000 dynamic volumes can be created at most. But the recommended number of dynamic volumes is 32 or even less.

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