EXT (Extended File System)
It was the first file system for Linux kernel developed by Remy Card in April 1992. It was based on metadata structure .It was the first file system that implemented VFS( Virtual File System ). Some features of this file system are as follows:
a) It supports maximum partition size up to 2 Giga Bytes.
b) It support file name size up to 255 characters long.
c) It lacked in timestamps (the current time of an event that is recorded by a computer) for modifications to inodes (a data Structure that stores all the information about a file except its name and its actual data) and to data.
d) It lacked in providing support for separate access for each user and group.
e) Linked list technique was used for file handling.
EXT2(The Second Extended File System)
It was initially developed by Remy card and was based on EXT file system but many new features and improved features were used in this. Some of the features of EXT2 file system are as follows:
a) Improved algorithm was used to increase its speed.
b) Improved Timestamp features was used that can save last file access date and last inode modification.
c) It provided the feature to track file system state.
d) Max. File size supported was 4TB.
e) Provide the feature of superblock that was a special field to mark status of file system as dirty or clean.
f) Files were saved in equal size block. E.g. 1030 byte file was saved on two 1024 byte blocks resulting in wastage of disk space.
g) It is not a journaling file system and does not maintain any journals that are used to minimize data corruption during power failure.
EXT3(The Third Extended File System)
It was developed by Mr. Stephen Tweedie and was introduced in November 2001(Linux 2.4.15).It was the extension EXT2 file system with the following new features:
a) It provided feature of Journals that keeps track of the changes before committing them to the main file system. During system crash or power failure, these file systems are quicker to bring back online and less likely to become corrupted.
b) It provides back support to EXT2 file system and allows upgrades without having to back up and restore data.
c) H-Tree indexing technique is used for storing large size directories.
d) It Support File size from 16 Gibibyte(1 gibibyte = 230 bytes = 1073741824 bytes = 1024 mebibytes) to 2 TebiByte(1 tebibyte = 240 bytes = 1099511627776 bytes = 1024 gibibytes)
e) Max. Volume size supported is 2 TiB – 16 TiB
f) There is no online fragmentation tool that work on file system level.
g) It does not provide support to recover deleted files.
h) Ext3 does not do check sum when writing to the journal.
i) A directory can have at most 31998 subdirectories, because an inode can have at most 32000 links.
EXT4(The Fourth Extended File System)
This file system is the extension for EXT3 file system. Some features of this file system are as follows
a) It support volume size up to 1 exbibyte(1 exbibyte = 260 bytes = 1152921504606846976 bytes = 1,024 pebibytes) and files size up to 16 TebiBytes(1 tebibyte = 240 bytes = 1099511627776 bytes = 1024 gibibytes).
b) Concept of Extent is implemented in this file system. Extent is a contiguous area of storage in a computer file system, reserved for a file. When a process creates a file, file-system management software allocates a whole extent.
c) It is backward compatible with ext2 and ext3 file system.
d) EXT4 file system can allocate pre-disk space a file.
e) It uses Delayed Allocation Technique that delays block allocation until it writes data to disk. This results in improved performance and also reduces.
f) It Support 64000 Sub Directories.
g) It makes use of Checksums for Journals.
h) It Provide fast file system check feature.
It was the first file system for Linux kernel developed by Remy Card in April 1992. It was based on metadata structure .It was the first file system that implemented VFS( Virtual File System ). Some features of this file system are as follows:
a) It supports maximum partition size up to 2 Giga Bytes.
b) It support file name size up to 255 characters long.
c) It lacked in timestamps (the current time of an event that is recorded by a computer) for modifications to inodes (a data Structure that stores all the information about a file except its name and its actual data) and to data.
d) It lacked in providing support for separate access for each user and group.
e) Linked list technique was used for file handling.
EXT2(The Second Extended File System)
It was initially developed by Remy card and was based on EXT file system but many new features and improved features were used in this. Some of the features of EXT2 file system are as follows:
a) Improved algorithm was used to increase its speed.
b) Improved Timestamp features was used that can save last file access date and last inode modification.
c) It provided the feature to track file system state.
d) Max. File size supported was 4TB.
e) Provide the feature of superblock that was a special field to mark status of file system as dirty or clean.
f) Files were saved in equal size block. E.g. 1030 byte file was saved on two 1024 byte blocks resulting in wastage of disk space.
g) It is not a journaling file system and does not maintain any journals that are used to minimize data corruption during power failure.
EXT3(The Third Extended File System)
It was developed by Mr. Stephen Tweedie and was introduced in November 2001(Linux 2.4.15).It was the extension EXT2 file system with the following new features:
a) It provided feature of Journals that keeps track of the changes before committing them to the main file system. During system crash or power failure, these file systems are quicker to bring back online and less likely to become corrupted.
b) It provides back support to EXT2 file system and allows upgrades without having to back up and restore data.
c) H-Tree indexing technique is used for storing large size directories.
d) It Support File size from 16 Gibibyte(1 gibibyte = 230 bytes = 1073741824 bytes = 1024 mebibytes) to 2 TebiByte(1 tebibyte = 240 bytes = 1099511627776 bytes = 1024 gibibytes)
e) Max. Volume size supported is 2 TiB – 16 TiB
f) There is no online fragmentation tool that work on file system level.
g) It does not provide support to recover deleted files.
h) Ext3 does not do check sum when writing to the journal.
i) A directory can have at most 31998 subdirectories, because an inode can have at most 32000 links.
EXT4(The Fourth Extended File System)
This file system is the extension for EXT3 file system. Some features of this file system are as follows
a) It support volume size up to 1 exbibyte(1 exbibyte = 260 bytes = 1152921504606846976 bytes = 1,024 pebibytes) and files size up to 16 TebiBytes(1 tebibyte = 240 bytes = 1099511627776 bytes = 1024 gibibytes).
b) Concept of Extent is implemented in this file system. Extent is a contiguous area of storage in a computer file system, reserved for a file. When a process creates a file, file-system management software allocates a whole extent.
c) It is backward compatible with ext2 and ext3 file system.
d) EXT4 file system can allocate pre-disk space a file.
e) It uses Delayed Allocation Technique that delays block allocation until it writes data to disk. This results in improved performance and also reduces.
f) It Support 64000 Sub Directories.
g) It makes use of Checksums for Journals.
h) It Provide fast file system check feature.
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