EXT2 File System in Unix/Linux: Extensions of File System Project

The simple EXT2 file system uses 1 KB block size and has only 1 disk block group. It can be extended easily as follows.

  • Multiple groups: The size of group descriptor is 32 bytes. With 1 KB block size, a block may contain 1024/32 = 32 group descriptors. With 32 groups, the file system size can be extended to 32*8 = 256 MB.
  • 4 KB block size: With 4 KB block size and only one group, the file system size would be 4*8 = 32 MB. With one group descriptor block, the file system may have 128 groups, which extend the file system size to 128*32 = 4GB. With 2 group descriptor blocks, the file system size would be 8GB, etc. Most of the extensions are straightforward, which are suitable topics for programming projects.
  • Pipe files: It’s possible to implement pipes as regular files, which obey the read/write protocol of pipes. The advantages of this scheme are: it unifies pipes and file inodes and it allows named pipes, which can be used by unrelated processes. In order to support fast read/write operations, pipe contents should be in memory, such as a RAMdisk. If desired, the reader may implement named pipes as FIFO files.
  • I/O Buffering: In the Programming Project, every disk block is read in or written out directly. This would incur too much physical disk I/O operations. For better efficiency, a real file system usually uses a set of I/O buffers as a cache memory for disk blocks. File system I/O buffering is covered in Chap. 12, but it may be incorporated into the file system project.

Source: Wang K.C. (2018), Systems Programming in Unix/Linux, Springer; 1st ed. 2018 edition.

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