tune2fs列出的inode blocks per group是什么意思？

查不到啊查不到。。。

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*   tune2fs -l /dev/sda3


tune2fs 1.41.14 (22-Dec-2010)  
...  
Block size: 4096  
Inodes per group: 8192  
Inode blocks per group: 256  
Inode size: 128  
...</p>
Inode blocks per group = Inode size * Inode per group / block size