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2010/03/18

Ext2 Vs ext3

Ext3 filesystem is nothing but next version of ext2 filesystem with journaling support. Ext3 has been structurally implemented same as ext2 so they have same data structures. he most important difference between Ext2 and Ext3 is that Ext3 supports journaling which allows fast recovery from disk problems. You also get reliability and a better performance with ext3. Ext3 is designed to take care of both metadata and data.

Ext3 is a tiny bit slower than ext2 is, but it holds tremendous advantages. There is really only one difference between ext2 and ext3, and that is that ext3 uses a journal to prevent filesystem corruption in the case of an unclean shutdown (ie. before the filesystem is synced to disk). That makes ext3 a bit slower than ext2 since all metadata changes are written to the journal, and then flushed to disk, but on the other hand you don't risk having the entire filesystem destroyed at power failure or if an unwitted person turns the computer off uncleanly.

Inode

Inode is a unique number given to a file in Unix OS. Every file in Unix has a inode number. Inodes store information of files, such as user and group ownership, access mode (read, write, execute permissions) and type of file. When a file system is created, data structures are created that contain information about files. Each file is associated with an inode that is identified by an inode number

File names and directory implications:

    * Inodes do not contain file names, only file metadata.
    * Unix directories are lists of "link" structures, each of which contains one filename and one inode number.
    * The kernel must search a directory looking for a particular filename and then convert the filename to the correct corresponding inode number if the name is found.


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