关于linux文件Blocks和Block size的一些解析

Dear 丶 2022-07-13 05:52 146阅读 0赞

### File system block sizes ###

On the other hand, every [file system][] needs to split up a [partition][] into blocks to store [files][] and file parts. This is why there is a different block size for a file system as you can see here:

tweedleburg:/mnt/sdb2 # stat -f .
      File: "."
        ID: 236d62321492c2ce Namelen: 255     Type: ext2/ext3
    Block size: 4096       Fundamental block size: 4096
    Blocks: Total: 76899893   Free: 8380419    Available: 4474114
    Inodes: Total: 39075840   Free: 38013010

So, if you store a file in this file system, it will be stored in a 4096-byte-block, that means, even if your file only contains 5 bytes, it will take away 4096 bytes from your disk's capacity:

tweedleburg:/mnt/sdb2 # df .
    Filesystem           1K-blocks      Used Available Use% Mounted on
    /dev/sdb2            307599572 274077896  17896456  94% /mnt/sdb2
    tweedleburg:/mnt/sdb2 # echo hallo>welt
    tweedleburg:/mnt/sdb2 # df .
    Filesystem           1K-blocks      Used Available Use% Mounted on
    /dev/sdb2            307599572 274077900  17896452  94% /mnt/sdb2
    tweedleburg:/mnt/sdb2 # du -csh welt
    4.0K    welt
    4.0K    total

摘自：[http://wiki.linuxquestions.org/wiki/Block\_devices\_and\_block\_sizes][http_wiki.linuxquestions.org_wiki_Block_devices_and_block_sizes]

小结：

1. **stat**命令输出的**Blocks**单位通常是**512bytes**，也就是一个扇区。

2. 一个文件假设只有几个字节，其实也会占用一个文件块(**Block size)**大小，通常是**4096bytes**。

3. 系统通常一次会读取一个**Block size**大小，而不是一个扇区大小。

原文出自：[http://blog.csdn.net/daiyudong2020/article/details/53897775][http_blog.csdn.net_daiyudong2020_article_details_53897775]

End;

[file system]: http://wiki.linuxquestions.org/wiki/File_system
[partition]: http://wiki.linuxquestions.org/wiki/Partition
[files]: http://wiki.linuxquestions.org/wiki/File
[http_wiki.linuxquestions.org_wiki_Block_devices_and_block_sizes]: http://wiki.linuxquestions.org/wiki/Block_devices_and_block_sizes
[http_blog.csdn.net_daiyudong2020_article_details_53897775]: http://blog.csdn.net/daiyudong2020/article/details/53897775