Window NT File System

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 Access method File management Auxiliary storage management File integrity mechanisms • Main types of the file system FAT HPFS NTFS • Window NT can support three types of file system FAT HPFS NTFS 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 The generated 8.3 filename is stored along with the long filename FAT partitions can be converted to NTFS Drive Size FAT Type (logical volume) (Floppy Disks) (Hard Disks) 16 128 256 512 1024 Cluster Per Cluster - Size - 360K 720K 1.2 MB 1.44 MB 2.88 MB 12-bit 12-bit 12-bit 12-bit 12-bit 2 1 1K 1K 512 bytes 512 bytes 1K MB MB MB MB MB MB 12-bit 16-bit 16-bit 16-bit 16-bit 16-bit 8 16 32 64 - 15 MB 127 MB 255 MB 511 MB 1023 MB 2048 MB Sectors 4K 2K 4K 8K 16K 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 Gigabytes (GB) under Windows NT and 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 HPFS File System • Origin of HPFS file system HPFS was introduced in 1990 as part of OS/2 Version 1.2 • Characters of HPFS HPFS allowed for greater capacity of hard drives HPFS also implements physical separation between files giving each file room for expansion, which would then result in less chance of fragmentation 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 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 NTFS is a recoverable file system because it keeps track of transactions against the file system 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 Not using special objects on the disk and tracking and protecting all objects that are on the disk Reliability(Cont.) 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 userdefined 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: Case Sensitive Naming Additional Time Stamp Hard Links 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 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 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 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 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 fileallocation table, in case one copy is damaged, it’s incapable of automatically fixing errors 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 Window NT(Should be used if you need to Dual-boot and access the partition from another OS)   No local security available   Does not support Macintosh files   Does not support NetWare file and directory permissions during NetWare migration   Does not support NT file compression   Can be converted to NTFS at any time   Maximum partition size of 4GB Only supported under the NT OS Local security is available Support Macintosh files Supports NetWare file and directory permission during migration Support NT file compression 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 16EB Reference Window NT Server Unleashed   Operating system Second Edition H M Deitel   http://magic.hurrah.com/~sabre/os/S3FileSystems/HPFS/hpfs0.html   http://support.microsoft.com/support/kb/articles/q100/1/18.asp   MCSE : NT Server in the Enterprise Second Edition L Donald, J Chellis