What is file
A file is the smallest allotment of logical secondary storage.
What is a file system
Files are managed by the operating system. The part of the operating system dealing with files & how they are structured, named, accessed, used, protected is known as File System.
Different types of File System
Windows File Systems
1. FAT(File allocation table):-
FAT was created by MICROSOFT in 1977.
Use as preffered file system for floppy disk
High capacity storage device like flash drive
Widely used in computer system & memory card used in digital cameras.
Version of FAT file system:-
FAT 12-The initial version of FAT introduced in 1977.
• Primary file system for Microsoft System upto MS-DOS 4.0
FAT 16-Introduced in 1988,primary file system for MS 4.0 upto Windows 95.
• Support drive size upto 2 GB.
FAT 32-Latest verson of FAT,introduced in 1996 for windows 95 OSRL Users.
• Support drive size upto 8TB.
FATxx volume division
FATxx volume is devided into four areas:-
The Boot record.
The file allocation table.
The root directory.
The data area.
• FAT starts with some marker
bits, and then consist of
A Cluster is a smallest logical amount
Of disk space that can be alloted to hold a file.
B. Geometrical sector
C. Track sector
Limitation Of FAT
FAT32 is not supported by every operating system.
Original version of Windows 95 couldn't read FAT 32.
Windows 2000 could not read FAT32 drives
New Technology File System(NTFS):-
NTFS is a new file system developed specially for windows NT.
Current version (version 5)
Windows NT 4.0
1. It uses 64-bit disk addresses and can support disk partitions up to 264 bytes.
2. Individual file names in NTFS are limited to 255 characters. Case sensitive names.
3. Encryption & Data recovery.
5. File level security.
Encrypting file system is used to encrypt files in NTFS.
Generally Public Key cryptography is used
It offers data recovery mechanism.
NTFS can perform data compression on individual files or on all data files in a directory.
NTFS allows file level security.With NTFS permissions ,one can control which users have what kind of access to which files.
Security can be assigned at two different levels
1. Per user basis
2. On a group basis
Network File System (NFS)
NFS is originally created by Sun Microsystems in 1984.
It is a widely used,well-implemented client server network file system.
It is used on all modern UNIX systems to join the file systems on separate computers.
Sharing file systems in a transparent manner.
Mounting remote file systems.
Exporting file systems.
Setting up NFS clients & servers involves starting the NFS daemons.
The /etc/exports file controls which files & directories are exported.
It also controls what kind of accessing are allowed.
NFS accomplishes two client-server protocol-
1. The Mount Protocol- it handles mounting.
2. The NFS protocols- which is for directory & file access.
NFS server daemons (nfsd)
Accept RPC calls from clients.
Run mounted daemon to handle request.
LINUX File System:-
Extended File Systems(extfs):-
The extended file system (ext), was released in April 1992 as the first file system using the VFS API and was included in Linux version 0.96c .
1) allowed 2 gigabytes of data
2) filenames of up to 255 characters.
Limitation of Ext:-
There was no support for separate access
i-node modification and data modification timestamps.
A new filesystems were developed in January 1993 by Rémy Card .
The second extended file system (ext2 )
The Second Extended File system was devised as an extensible and powerful file system for Linux. It is also the most successful file system so far in the Linux community and is the basis for all of the currently shipping Linux distributions.
Ext2 data structures
Physical Layout of the EXT2 File system
i-node structure of ext-2:-
Features of ext -2
POSIX ,ACL and extended attribute were first introduced.
Journaling not allowed with flash drives.
Limit of sublevel directory 32768
Cannot handle file larger than 2TB
Block size is limited by architecture
Developer Stephen Tweedie
Introduced November 2001
Advantages of ext-3
A journal file system
H-tree indexing for larger directory
No checksumming in journal..
1) Modern Operating Systems: A S Tanenabum.
2) Operating System Concepts: Silberschatz;Galvin;Gagne.
5) "Design and implementation of the second extended filesystem