文件系统：ext4 的 block 分布（1G分区为例)

总的block数量：262144

$ dumpe2fs /dev/vg01/test  | grep "Block count"
dumpe2fs 1.42.9 (28-Dec-2013)
Block count:              262144

减去数据块数： 249830，剩下：12314

$ df -B 4k /mnt
Filesystem            4K-blocks  Used Available Use% Mounted on
/dev/mapper/vg01-test    249830   641    231986   1% /mnt

总的Inode数量 * 每个Inode大小，计算得到block数：4096，相减剩下：8218

$ dumpe2fs /dev/vg01/test  | grep "Inode count"
dumpe2fs 1.42.9 (28-Dec-2013)
Inode count:              65536

$ dumpe2fs /dev/vg01/test  | grep "Inode size"
dumpe2fs 1.42.9 (28-Dec-2013)
Inode size:               256

8个块组，每个块组两个位图，使用block数：16，相减剩下：8202

$ dumpe2fs /dev/vg01/test  | grep "Group" | grep Blocks
dumpe2fs 1.42.9 (28-Dec-2013)
Group 0: (Blocks 0-32767) [ITABLE_ZEROED]
Group 1: (Blocks 32768-65535) [INODE_UNINIT, ITABLE_ZEROED]
Group 2: (Blocks 65536-98303) [INODE_UNINIT, BLOCK_UNINIT, ITABLE_ZEROED]
Group 3: (Blocks 98304-131071) [INODE_UNINIT, ITABLE_ZEROED]
Group 4: (Blocks 131072-163839) [INODE_UNINIT, ITABLE_ZEROED]
Group 5: (Blocks 163840-196607) [INODE_UNINIT, ITABLE_ZEROED]
Group 6: (Blocks 196608-229375) [INODE_UNINIT, BLOCK_UNINIT, ITABLE_ZEROED]
Group 7: (Blocks 229376-262143) [INODE_UNINIT, ITABLE_ZEROED]

5个superblock（包括4个backup）+ 5个 Group descriptors：10，相减剩下：8192

$ dumpe2fs /dev/vg01/test  | grep "superblock"
dumpe2fs 1.42.9 (28-Dec-2013)
  Primary superblock at 0, Group descriptors at 1-1
  Backup superblock at 32768, Group descriptors at 32769-32769
  Backup superblock at 98304, Group descriptors at 98305-98305
  Backup superblock at 163840, Group descriptors at 163841-163841
  Backup superblock at 229376, Group descriptors at 229377-229377

ext4的日志系统使用block数：8192，计算完毕。

$ dumpe2fs /dev/vg01/test  | grep Journal
dumpe2fs 1.42.9 (28-Dec-2013)
Journal inode:            8
Journal backup:           inode blocks
Journal features:         journal_64bit
Journal size:             32M
Journal length:           8192
Journal sequence:         0x00000002
Journal start:            1