本經驗均在CentOSrelease6.7(Final)下操作，如知識有欠缺之處 歡迎批評指正。
linux 的inode及block的相關知識：
1> Linux系統分區格式化文件系統之后，系統會分為Inode及Block兩部分：
1)Inode為系統文件的屬性信息（ls -l的結果）及指向文件實體的指針，但是沒有存放文件名，一般在上級目錄里的Block。
2)Block為存放數據的，ext3/ext4一般為1k,2k,4k,一般默認4k
3)一個文件不論多大至少占用一個Inode和一個Block，一個Block只能存放一個文件的內容，block的數量大于Inode的數量，多個文件可以占用同一個 inode(硬鏈接) 。
4）訪問文件, 通過文件-->inode(驗證權限)--->blocks.
5）inode 一般情況默認256B，block大小1k，2k，4k，默認4k,注意，引導分區等特殊分區除外。
6）通過df -i 查看inode的數量及使用情況,dumpe2fs /dev/sda1 查看inode及block的大小和數量。
7）一個block只能 被一個文件使用 ，如果一個文件很小block太大，剩余空間浪費，無法繼續被其他文件使用。
8）block不是越大越好，根據業務的文件大小進行選擇，一般就是默認 4k。
9）可以在格式化的時候改變inode及block的大小，使用mkfs.ext4 -b 2048 -I 1024 /dev/sdb2
2>Linux中df命令的功能是用來檢查linux服務器的文件系統的磁盤空間占用情況。可以利用該命令來獲取硬盤被占用了多少空間，目前還剩下多少空間等信息。
1．命令格式：
df [選項] [文件]
2.參數 :
df -i 查看參數多少個
[root@techW ~]# df -i
Filesystem Inodes IUsed IFree IUse% Mounted on
/dev/mapper/vg_techw-lv_root
1152816 55846 1096970 5% /
tmpfs 125596 1 125595 1% /dev/shm
/dev/sda1 128016 38 127978 1% /boot
df -h 查看磁盤大小：
[root@techW ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_techw-lv_root
18G 1.5G 15G 9% /
tmpfs 491M 0 491M 0% /dev/shm
/dev/sda1 477M 36M 416M 8% /boot
查看當前系統分區的Inode及Block的總量及使用量：
[root@techW ~]# dumpe2fs /dev/sda1 | grep -i "block size"
dumpe2fs 1.41.12 (17-May-2010)
Block size: 1024
[root@techW ~]#
[root@techW ~]#
[root@techW ~]# dumpe2fs /dev/sda1 | grep -i "inode size"
dumpe2fs 1.41.12 (17-May-2010)
Inode size: 128 ###boot分區為128，常規分區為256
[root@techW ~]#
[root@techW ~]#
[root@techW ~]# dumpe2fs /dev/sda1 | grep -i "inode count"
dumpe2fs 1.41.12 (17-May-2010)
Inode count: 128016
[root@techW ~]#
[root@techW ~]# dumpe2fs /dev/sda1 | grep -i "block count"
dumpe2fs 1.41.12 (17-May-2010)
Block count: 512000
Reserved block count: 25600
3>添加一塊磁盤，格式化，改變Inode及 Block的大小，掛載查看硬盤的Inode及Block數量：
1）添加一塊5G的磁盤，為方便區分設置為/dev/sdb，fdisk分區，然后mkfs.ext4格式化
（虛擬機增加一塊5G的硬盤，分區，格式化）
[root@techW ~]# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x2d37eabe.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help): n ### add a new partition
Command action
e extended
p primary partition (1-4)
p
Partition number (1-4): 2 ### 為做區分，選擇2
First cylinder (1-652, default 1):
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-652, default 652):
Using default value 652
Command (m for help): w ### write table to disk and exit
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
分區時的參數命令：
a toggle a bootable flag
b edit bsd disklabel
c toggle the dos compatibility flag
d delete a partition
l list known partition types
m print this menu
n add a new partition
o create a new empty DOS partition table
p print the partition table
q quit without saving changes
s create a new empty Sun disklabel
t change a partition's system id
u change display/entry units
v verify the partition table
w write table to disk and exit
x extra functionality (experts only)
[root@techW ~]# mkfs.ext4 /dev/sdb2
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2) ###默認的Block的大小為4096
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
327680 inodes, 1309289 blocks
65464 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1342177280
40 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912, 819200, 884736
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 26 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
2）###inode的大小范圍為128-2048,block的大小范圍為1024-4096####
3)將Block和Inode的大小都改為2048：
[root@techW ~]# mkfs.ext4 -b 2048 -I 2048 /dev/sdb2
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=2048 (log=1)
Fragment size=2048 (log=1)
Stride=0 blocks, Stripe width=0 blocks
326400 inodes, 2618578 blocks
130928 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=540016640
160 block groups
16384 blocks per group, 16384 fragments per group
2040 inodes per group
Superblock backups stored on blocks:
16384, 49152, 81920, 114688, 147456, 409600, 442368, 802816, 1327104,
2048000
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 30 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
4)使用dumpe2fs命令查詢Inode和Block的大小：
[root@techW ~]# dumpe2fs /dev/sdb2 | grep "Inode size"
dumpe2fs 1.41.12 (17-May-2010)
Inode size: 2048 ###大小更改成功
[root@techW ~]#
s /dev/sdb2 | grep "Block size"
dumpe2fs 1.41.12 (17-May-2010)
Block size: 2048 ###大小更改成功
