ext file system

ext file system
1. A system called an inode is used to store information about files stored in a virtual directory.
2. The inode system creates a separate table (called an inode table) in each physical device to store information about these files.
3. Each file stored in the virtual directory has an entry in the inode table

Disadvantages :
1. The file size cannot exceed 2 GB
2. The blocks used to store data are easily scattered throughout the device (called fragmentation, fragmentation) Fragmentation of data blocks will reduce the performance of the


file system ext2 file system 1. The ext2 file
system is an extension of the basic function of the ext file system, but maintains the same structure. The ext2 file system extends the format of the inode table to hold more information about each file on the system 2. The inode table of ext2
adds creation time, modification time and last access time values ​​to files
to track File access situation 3. The
ext2 file system also increases the maximum allowable file size to 2 TB

Disadvantages:
1. The ext2 file system is easily damaged in the event of a system crash or power failure
2. Even if the file data is normally saved to a physical device, if If the inode table record is not updated, the ext2 file system does not even know that the
file


exists
, the first write operation is to operate the log record file
2. If the entire write operation is interrupted for some reason (such as system power failure), when the system restarts, the write operation before the interruption will be resumed according to the log record, and this process is time-consuming extremely short
3. The ext3 file system uses the log function of the ordered mode - only the inode information is written to the log file, and it is not deleted until the data blocks are successfully written to the storage device.

Disadvantages :
1. The ext3 file system cannot recover accidentally deleted files
2 .It does not have any built-in data compression function (although there is a patch that needs to be installed separately to support this function)
3. Does not support encrypted files


The ext4 file system was officially supported by the Linux kernel in 2008 and is now the most popular Linux distribution The default file system used by the version
1. Supports data compression and encryption
2. The ext4 file system also supports a feature called extent. Sections allocate space in blocks on the storage device, but only save the location of the starting block in the inode table.
3. Introduced block preallocation technology (block preallocation) The file reserved space, the ext4 file system can allocate all needed blocks for the file, not just those blocks that are already in use. The ext4 filesystem fills up reserved data blocks with 0s and does not allocate them to other files