NTFS is a high-performance and self-healing file system proprietary to Windows XP Vista 2003,2000, NT & Windows 7, which supports file-level security, compression and auditing. It also supports large volumes and powerful storage solution such as RAID. The most important new feature of NTFS is the ability to encrypt files and folders to protect your sensitive data.
NTFS is a Microsoft file system. It was introduced in Windows NT and has been the default file system for every version of Microsoft Windows since. NTFS replaced the aged FAT file system and addresses most of FAT's shortcomings. NTFS has been continuously maintained and improved by Microsoft, and the current version provides secure data storage that meets the requirements of modern hardware and usage. However, NTFS remains a closed standard, Microsoft does not publish its API nor implementation details. Therefore only Microsoft operating systems can use NTFS natively, and even OS's that are capable of reading and writing to NTFS cannot be installed on hard disks formatted as NTFS.
The NTFS acronym stands for New Technology File System. The name derives from the implementation of very innovative data storage techniques that were refined in NTFS. While none of the techniques are unique to NTFS, it is the first time that so many innovations were released at once on a production file system. The FAT file system had long been criticized for not including some of the more obvious improvements such as journaling, disk quotas, and file compression. However, these improvements made NTFS incompatible with previous versions of Windows, and also with hard disk tools designed for FAT file systems. For example, data recovery tools such as GetDataBack and partitioning tools such as PartitionMagic would run on Windows NT, yet could not function on the newer file system. This led to much frustration with users who had purchased licenses for these products before upgrading to Windows NT.
NTFS Master File Table (MFT)
Each file on an NTFS volume is represented by a record in a special file called the master file table (MFT). NTFS reserves the first 16 records of the table for special information. The first record of this table describes the master file table itself, followed by a MFT mirror record. If the first MFT record is corrupted, NTFS reads the second record to find the MFT mirror file, whose first record is identical to the first record of the MFT. The locations of the data segments for both the MFT and MFT mirror file are recorded in the boot sector. A duplicate of the boot sector is located at the logical center of the disk.
The third record of the MFT is the log file, used for file recovery. The seventeenth and following records of the master file table are for each file and directory (also viewed as a file by NTFS) on the volume.
Metafiles
The first 16 NTFS files (metafiles) are system files. Each of them is responsible for some aspect of system operation. The advantage of such modular approach is in amazing flexibility - for example on FAT the physical failure in the FAT area is fatal for all disk operation. As for NTFS it can displace and even fragment on the disk all system areas avoiding any damage of the surface except the first 16 MFT elements.
The metafiles are in the NTFS disk root directory, they start with a name character "$", though it is difficult to get any information about them by standard means. Curiously that even for these files the quite real size is reported, and it is possible to find out for example how many operating system spends on cataloguing of all your disk having looked at $MFT file size. In the following table the metafiles used at the moment and their function are indicated.
Files and streams
So the system has files and nothing except files. What does this concept on NTFS include?
First of all the compulsory element is the record in MFT. As it was said above all disk files are mentioned in MFT. All information about a file except data itself is stored in this place: a file name, its size, separate fragments position on the disk, etc. If one MFT record is not enough for information, then several records are used and not obligatory one after another. Optional element is file data streams. The definition "optional" seems to be a bit strange but nevertheless there is nothing strange here. Firstly a file may not have data and in this case disk free space isn't used on it. Secondly a file may have not very big size. Then a rather successful decision is applied: file data are stored just in MFT, in the place free from the master data in limits of one MFT record. The files with the size of hundreds byte usually don't have "physical" image in the fundamental file area. All such file data are stored in one place - in MFT.
The directories
The directory on NTFS is a specific file storing the references to other files and directories establishing the hierarchical constitution of disk data. The directory file is divided into blocks, each of them contains a file name, base attributes and reference to the element MFT which already gives the complete information on an element of the directory. The inner structure of the directory is a binary tree. It means that to search the file with the given name in the linear directory such for example as for FAT, the operating system should look through all elements of the directory until it finds the necessary one. The binary tree allocates the names of files to make the file search faster - with the help of obtaining binary answers to the questions about the file position. The binary tree is capable to give the answer to the question in what group the required name is situated - above or below the given element. We begin with such question to the average element, and each answer narrows the area of search twice. The files are sorted according to the alphabet, and the answer to the question is carried out by the obvious way - matching of initial letters. The search area which has been narrowed twice starts to be researched the same way starting again from the average element.
FAT
The FAT file system was first introduced in the days of MS-DOS way back in 1981. The purpose of the File Allocation Table is to provide the mapping between clusters - the basic unit of logical storage on a disk at the operating system level - and the physical location of data in terms of cylinders, tracks and sectors - the form of addressing used by the drive's hardware controller.
The FAT contains an entry for every file stored on the volume that contains the address of the file's starting cluster. Each cluster contains a pointer to the next cluster in the file, or an end-of-file indicator at (0xFFFF), which indicates that this cluster is the end of the file. The diagram shows three files: File1.txt uses three clusters, File2.txt is a fragmented file that requires three clusters and File3.txt fits in one cluster. In each case, the file allocation table entry points to the first cluster of the file.
The FAT16 file system is compatible with the majority of operating systems. This is evident by MS DOS, Windows 95, Windows 98, Windows Me, Windows NT, Windows 2000 and Windows XP being able to utilize the FAT16 file system. FAT16 generally works well in managing disk space when the size of the volume is less than 256MB. You should refrain from using FAT16 on volumes that are larger than 512MB. FAT16 cannot be utilized on volumes that exceed 4 GB.
FAT16 maps clusters on the FAT partition. A cluster is the smallest unit that the OS operating system utilizes when it assigns space on the partition. A cluster is also at times referred to as an allocation unit.
The file allocation table identifies a cluster in the FAT partition as either:
• Unused
• Cluster in use by a file
• Bad cluster
• Last cluster in a file
The FAT16 volume is structured as follows:
• Boot sector on the system partition
• The primary file allocation table
• The copy or duplicate file allocation table
• A root folder
• Other folders and all files
The root folder holds an entry for each file and folder stored on the FAT16 volume and has its maximum number of table entries set at 512 for each disk drive. A file's or folder's entry contains the information listed below:
• Name: This is in 8.3 format
• Attribute: 8 bits
• Create time: 24 bits
• Create date: 16 bits
• Last access date: 16 bits
• Last modified time: 16 bits
• Last modified date: 16 bits
• Starting cluster number in the file allocation table: 16 bits
• File size: 32 bits
Disavantages of FAT16
A few disadvantages associated with the FAT16 file system are summarized below:
• The FAT16 file system has no local security for the file system or compression features.
• The boot sector is not backed up.
• The root folder can only have a maximum of 512 entries which means that files which have long names can greatly decrease the number of entries available.
• FAT16 does not work well with volume sizes that are large.
The FAT32 File System
The FAT32 file system can handle larger partitions than what the FAT16 file system can handle. FAT32 can support partitions up to 2047 GB in size compared to FAT16's 4 GB. With FAT32, there is no restriction on the number of entries that the root folder can contain. With FAT16, the root folder could only contain a maximum of 512 entries. The boot sector is also backed up on FAT32 volumes. A FAT32 volume must however have a minimum of 65,527 clusters.
The FAT32 architecture is very much like the architecture of the FAT16 file system. FAT32 was designed with little architectural changes to ensure compatibility with existing programs and device drivers. What this means is that device drivers and FAT tools used for FAT16 partitions would continue to work for FAT32 partitions.
FAT32 does however need 4 bytes in the file allocation table to store cluster values. This has led to the revision or expansion of internal data structures, on-disk data structures and published APIs.
A few disadvantages associated with the FAT32 file system are summarized below:
• Like the FAT16 file system, the FAT32 file system includes no local security for the files system or compression features.
• The MS-DOS, Windows 95, and Windows NT 4.0 OSs are unable to access or read FAT32 partitions.
• Both FAT16 and FAT32 partitions do not scale well - the file allocation table increases in size as the volume grows.
NTFS vs FAT
NTFS vs FAT32
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