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This article mainly introduces "what are the differences between ex3 and ex4 in linux". In daily operation, I believe many people have doubts about the differences between ex3 and ex4 in linux. The editor consulted all kinds of materials and sorted out simple and easy-to-use methods of operation. I hope it will be helpful to answer the questions of "what are the differences between ex3 and ex4 in linux?" Next, please follow the editor to study!

Differences: 1, the ext3 file system for 16TB, and ext4 for 1EBter2, ext3 subdirectories can have 32000, and ext4 subdirectories can be an unlimited number; 3, ext4 operation efficiency of large files than ext3; 4, data block allocation strategy, ext3 is allocated as soon as possible, and ext4 is delayed allocation.

The operating environment of this tutorial: linux5.9.8 system, Dell G3 computer.

The difference between ex3 and ex4 in linux

1. Larger file systems and larger files

Ext3:16TB file system and maximum 2TB file, ext4:1EB file system and maximum 16TB file.

2. Unlimited number of subdirectories

Ext3:32000 subdirectories, ext4: an unlimited number of subdirectories.

3 、 Extents

Ext3 uses indirect block mapping, which is extremely inefficient when manipulating large files. For example, for a 100MB-sized file, you need to create a mapping table of 25600 blocks (each of which is 4KB) in ext3.

While ext4 introduces the concept of extents, each extent is a set of continuous data blocks, and the above file is expressed as "the file data is saved in the next 25600 data blocks", which improves a lot of efficiency.

4. Multi-block allocation

Ext3's block allocator can only allocate one 4KB block at a time. Writing a 100MB file calls the 25600-degree data block allocator, while ext4's multi-block allocator "multiblock allocator" (mballoc) supports the allocation of multiple blocks in one call.

5. Delayed allocation

Ext3's block allocation strategy is to allocate as soon as possible, while ext4 delays allocation as much as possible, and does not start allocating blocks and writing to disk until the file has been written in cache, so that block allocation for the entire file can be optimized and performance can be significantly improved when combined with the first two features.

6. Related characteristics of inode

Ext3:128byte,ext4:256byte .

At this point, the study on "what is the difference between ex3 and ex4 in linux" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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