Window NT File System JianJing Cao (#98284)

Contents Introduction FAT File System HPFS File System NTFS File System Compare FAT File System with NTFS File System

Introduction Function of file system 1. Access method 2. File management 3. Auxiliary storage management 4. File integrity mechanisms Main types of the file system 1. FAT 2. HPFS 3. NTFS Window NT can support three types of file system No other operating system has as many choices for file system as does Windows NT.

FAT File System Origin of FAT file system A disk formatted with FAT is allocated in clusters (size are determined by the size of the volume ) FAT is handled slightly differently under NT. 1. The generated 8.3 filename is stored along with the long filename 2. FAT partitions can be converted to NTFS The Fat was invented by Bill Gates and Marc McDonald in 1997 as a method of managing disk space in the NCR version of standalone Microsoft Disk BASIC The FAT file system is also prone to fragmentation, which is the result of data being written to noncontiguous clusters, which can slow down the read/write process

Drive Size FAT Type Sectors Cluster (logical volume) Per Cluster Size ---------------- -------- ----------- ------- (Floppy Disks) 360K 12-bit 2 1K 720K 12-bit 2 1K 1.2 MB 12-bit 1 512 bytes 1.44 MB 12-bit 1 512 bytes 2.88 MB 12-bit 2 1K (Hard Disks) 0 MB - 15 MB 12-bit 8 4K 16 MB - 127 MB 16-bit 4 2K 128 MB - 255 MB 16-bit 8 4K 256 MB - 511 MB 16-bit 16 8K 512 MB - 1023 MB 16-bit 32 16K 1024 MB - 2048 MB 16-bit 64 32K

Advantages of FAT File System The FAT file system is best for drives and/or partitions under approximately 200 MB It is better to format system partition as FAT

Disadvantage of FAT File System It is advisable to not use FAT on partitions that are greater than 200 megabytes. FAT partitions are limited in size to a maximum of 4 Gigabytes (GB) under Windows NT and 2 GB in MS-DOS. It is not possible to set permissions on files that are FAT partitions.

Disadvantage of FAT File System(Con.) Any FAT partitions that use DOS-based disk compression (such as Stacker or DriveSpace) will not have readable files when running Windows NT The FAT file system is also prone to fragmentation which is the result of data being written to noncontiguous clusters, which can slow down the read/write process

HPFS File System Origin of HPFS file system HPFS was introduced in 1990 as part of OS/2 Version 1.2 Characters of HPFS 1. HPFS allowed for greater capacity of hard drives 2. HPFS also implements physical separation between files giving each file room for expansion, which would then result in less chance of fragmentation 3. HPFS also introduced long filenames of up to 255 characters, along with other attributes

Advantage of HPFS HPFS is best for drives in the 200-400 MB range. Less chance of fragment

Disadvantage of HPFS Because of the overhead involved in HPFS, it is not a very efficient choice for a volume of under approximately 200 MB. With volumes larger than about 400 MB, there will be some performance degradation. You cannot set security on HPFS under Windows NT. HPFS is only supported under Windows NT versions 3.1, 3.5, and 3.51. Windows NT 4.0 can not access HPFS partitions.

NTFS File System Origin of NTFS File System With the introduction of Windows NT in 1992, Microsoft took the advanced capabilities of HPFS and went many steps further

The Goals of NTFS Reliability, which is especially desirable for high end systems and file servers A platform for added functionality Support POSIX requirements Removal of the limitations of the FAT and HPFS file systems

Reliability Recoverability 1. NTFS is a recoverable file system because it keeps track of transactions against the file system. 2. Under NTFS, a log of transactions against these components is maintained so that CHKDSK need only roll back transactions to the last commit point in order to recover consistency within the file system. Removal of fatal single sector failures 1. Not using special objects on the disk and tracking and protecting all objects that are on the disk When a CHKDSK is performed on FAT or HPFS, the consistency of pointers within the directory, allocation, and file tables is being checked Under FAT or HPFS, if a sector that is the location of one of the file system's special objects fails, then a single sector failure will occur.

Reliability(Cont.) Hot fixing 2. Under NTFS, multiple copies (the number depends on the volume size) of the Master File Table are kept. Hot fixing Similar to OS/2 versions of HPFS, NTFS supports hot fixing.

Added Functionality NTFS provides a rich and flexible platform for other file systems to be able to use NTFS fully supports the Windows NT security model and supports multiple data streams. No longer is a data file a single stream of data. Under NTFS, a user can add his or her own user-defined attributes to a file.

POSIX Support NTFS is the most POSIX.1 compliant of the supported file systems because it supports the following POSIX.1 requirements: 1. Case Sensitive Naming 2. Additional Time Stamp 3. Hard Links The additional time stamp supplies the time at which the file was last accessed. A hard link is when two different filenames, which can be located in different directories, point to the same data.

Removing Limitations NTFS has greatly increased the size of files and volumes, so that they can now be up to 16 exabytes NTFS has also returned to the FAT concept of clusters in order to avoid HPFS problem of a fixed sector size. In NTFS all filenames are Unicode based, and 8.3 filenames are kept along with long filenames Therefore, 512 bytes per sector was viewed as having a large possibility of not always being a good fit for the allocation.

Advantages of NTFS Large disks and large files :NTFS is best for use on volumes of about 400 MB or more Recoverability: The recoverability designed into NTFS is such that a user should never have to run any sort of disk repair utility on an NTFS partition. Security: NTFS uses the Windows NT object model to enforce security. An open file is implemented as a file object with a security descriptor that defines its security attributes. General indexing facility: NTFS associates a collection of attributes with each file. The set of file descriptions in the file management system is organized as a relational database, so that files can be indexed by any attribute.

Advantages of NTFS(Cont.) Multiple data stream: be used by remote Macintosh systems to store and retrieve files On Macintosh, each file has two components: the file data and a resource fork that contains information about the file. NTFS treats these two components as two data streams.

Disadvantages of NTFS It is not recommended to use NTFS on a volume that is smaller than approximately 400 MB Currently, there is no file encryption built into NTFS It is not possible to format a floppy disk with the NTFS file system someone can boot under MS-DOS, or another operating system, and use a low-level disk editing utility to view data stored on an NTFS volume.

Compare FAT and NTFS File System Compatibility Only Windows NT supports NTFS partitions , Windows NT and Windows 95 supports both NTFS and FAT Volume size FAT supports partition sizes only up to 2 GB , the maximum size of an NTFS partition is 16 EB Fault tolerance Windows NT offers software support for several alternate disk-access methods that increase speed and/or fault tolerance, While FAT does maintain two copies of the file-allocation table, in case one copy is damaged, it’s incapable of automatically fixing errors Instead, you must run a utility such as Scandisk

Compare FAT and NTFS File System(Cont.) Security NTFS has a built-in security system , FAT has no local protection, it only has the share permission(protect the file from network) File compression NTFS has its native support for file compression, It offers you the chance to compress individual files and directories of your choice

Compare FAT and NTFS File System(Cont.) The system partition A better solution is to format your system partition as FAT because NTFS partitions are accessible only via Windows NT. If you have a fatal error with Windows NT, you can’t simply boot a system disk to a command prompt and fix a problem on an NTFS partition Converting to NTFS In MS-DOS type command: CONVERT drive: /FS:NTFS

FAT NTFS   Support by DOS, OS/2, Windows 95, and Only supported under the NT OS Window NT(Should be used if you need to Dual-boot and access the partition from another OS) No local security available Local security is available Does not support Macintosh files Support Macintosh files Does not support NetWare file and directory Supports NetWare file and directory permissions during NetWare migration permission during migration Does not support NT file compression Support NT file compression Can be converted to NTFS at any time NTFS can never be converted to FAT. The only way to go from NTFS to FAT is to backup the data, reformat the partition as FAT, and then restore the data to the new FAT partition. Maximum partition size of 4GB Maximum partition size of 16EB

Reference 1. Window NT Server Unleashed   2. Operating system Second Edition H. M. Deitel 3. http://magic.hurrah.com/~sabre/os/S3FileSystems/HPFS/hpfs0.html 4. http://support.microsoft.com/support/kb/articles/q100/1/18.asp 5. MCSE : NT Server 4 in the Enterprise Second Edition L. Donald, J. Chellis