<p>本经验均在CentOSrelease6.7(Final)下操作，如知识有欠缺之处 欢迎批评指正。</p><p>linux 的inode及block的相关知识：</p><p>1> Linux系统分区格式化文件系统之后，系统会分为Inode及Block两部分：</p><p>1)Inode为系统文件的属性信息（ls -l的结果）及指向文件实体的指针，但是没有存放文件名，一般在上级目录里的Block。</p><p>2)Block为存放数据的，ext3/ext4一般为1k,2k,4k,一般默认4k</p><p>3)一个文件不论多大至少占用一个Inode和一个Block，一个Block只能存放一个文件的内容，block的数量大于Inode的数量，多个文件可以占用同一个 inode(硬链接) 。</p><p>4）访问文件, 通过文件-->inode(验证权限)--->blocks.</p><p>5）inode 一般情况默认256B，block大小1k，2k，4k，默认4k,注意，引导分区等特殊分区除外。</p><p>6）通过df -i 查看inode的数量及使用情况,dumpe2fs /dev/sda1 查看inode及block的大小和数量。</p><p>7）一个block只能 被一个文件使用 ，如果一个文件很小block太大，剩余空间浪费，无法继续被其他文件使用。</p><p>8）block不是越大越好，根据业务的文件大小进行选择，一般就是默认 4k。</p><p>9）可以在格式化的时候改变inode及block的大小，使用mkfs.ext4 -b 2048 -I 1024 /dev/sdb2</p><p>2>Linux中df命令的功能是用来检查linux服务器的文件系统的磁盘空间占用情况。可以利用该命令来获取硬盘被占用了多少空间，目前还剩下多少空间等信息。</p><p>1．命令格式：</p><p>df [选项] [文件]</p><p>2.参数 :</p><p>df -i 查看参数多少 个</p><pre class="brush:cpp;toolbar:false">[root@techW~]#df-i
FilesystemInodesIUsedIFreeIUse%Mountedon
/dev/mapper/vg_techw-lv_root
11528165584610969705%/
tmpfs12559611255951%/dev/shm
/dev/sda1128016381279781%/boot</pre><p>df -h 查看磁盘大小：</p><pre class="brush:cpp;toolbar:false">[root@techW~]#df-h
FilesystemSizeUsedAvailUse%Mountedon
/dev/mapper/vg_techw-lv_root
18G1.5G15G9%/
tmpfs491M0491M0%/dev/shm
/dev/sda1477M36M416M8%/boot</pre><p>查看当前系统分区的Inode及Block的总量及使用量：</p><p>[root@techW ~]# dumpe2fs /dev/sda1 | grep -i "block size"</p><pre class="brush:cpp;toolbar:false">dumpe2fs1.41.12(17-May-2010)
Blocksize:1024
[root@techW~]#
[root@techW~]#
[root@techW~]#dumpe2fs/dev/sda1|grep-i"inodesize"
dumpe2fs1.41.12(17-May-2010)
Inodesize:128###boot分区为128，常规分区为256
[root@techW~]#
[root@techW~]#
[root@techW~]#dumpe2fs/dev/sda1|grep-i"inodecount"
dumpe2fs1.41.12(17-May-2010)
Inodecount:128016
[root@techW~]#
[root@techW~]#dumpe2fs/dev/sda1|grep-i"blockcount"
dumpe2fs1.41.12(17-May-2010)
Blockcount:512000
Reservedblockcount:25600</pre><p>3>添加一块磁盘，格式化，改变Inode及 Block的大小，挂载查看硬盘的Inode及Block数量：</p><p>1）添加一块5G的磁盘，为方便区分设置为/dev/sdb，fdisk分区，然后mkfs.ext4格式化</p><p>（虚拟机增加一块5G的硬盘，分区，格式化）</p><p>[root@techW ~]# fdisk /dev/sdb</p><p>Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel</p><p>Building a new DOS disklabel with disk identifier 0x2d37eabe.</p><p>Changes will remain in memory only, until you decide to write them.</p><p>After that, of course, the previous content won't be recoverable.</p><p>Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)</p><p>WARNING: DOS-compatible mode is deprecated. It's strongly recommended to</p><p> switch off the mode (command 'c') and change display units to</p><p> sectors (command 'u').</p><p>Command (m for help): n ### add a new partition</p><p>Command action</p><p> e extended</p><p> p primary partition (1-4)</p><p>p</p><p>Partition number (1-4): 2 ### 为做区分，选择2</p><p>First cylinder (1-652, default 1):</p><p>Using default value 1</p><p>Last cylinder, +cylinders or +size{K,M,G} (1-652, default 652):</p><p>Using default value 652</p><p>Command (m for help): w ### write table to disk and exit</p><p>The partition table has been altered!</p><p>Calling ioctl() to re-read partition table.</p><p>Syncing disks.</p><p>分区时的参数命令：</p><p> a toggle a bootable flag</p><p> b edit bsd disklabel</p><p> c toggle the dos compatibility flag</p><p> d delete a partition</p><p> l list known partition types</p><p> m print this menu</p><p> n add a new partition</p><p> o create a new empty DOS partition table</p><p> p print the partition table</p><p> q quit without saving changes</p><p> s create a new empty Sun disklabel</p><p> t change a partition's system id</p><p> u change display/entry units</p><p> v verify the partition table</p><p> w write table to disk and exit</p><p> x extra functionality (experts only)</p><pre class="brush:cpp;toolbar:false">[root@techW~]#mkfs.ext4/dev/sdb2
mke2fs1.41.12(17-May-2010)
Filesystemlabel=
OStype:Linux
Blocksize=4096(log=2)###默认的Block的大小为4096
Fragmentsize=4096(log=2)
Stride=0blocks,Stripewidth=0blocks
327680inodes,1309289blocks
65464blocks(5.00%)reservedforthesuperuser
Firstdatablock=0
Maximumfilesystemblocks=1342177280
40blockgroups
32768blockspergroup,32768fragmentspergroup
8192inodespergroup
Superblockbackupsstoredonblocks:
32768,98304,163840,229376,294912,819200,884736
Writinginodetables:done
Creatingjournal(32768blocks):done
Writingsuperblocksandfilesystemaccountinginformation:done
Thisfilesystemwillbeautomaticallycheckedevery26mountsor
180days,whichevercomesfirst.Usetune2fs-cor-itooverride.</pre><p>2）###inode的大小范围为128-2048,block的大小范围为1024-4096####</p><p>3)将Block和Inode的大小都改为2048：</p><pre class="brush:cpp;toolbar:false">[root@techW~]#mkfs.ext4-b2048-I2048/dev/sdb2
mke2fs1.41.12(17-May-2010)
Filesystemlabel=
OStype:Linux
Blocksize=2048(log=1)
Fragmentsize=2048(log=1)
Stride=0blocks,Stripewidth=0blocks
326400inodes,2618578blocks
130928blocks(5.00%)reservedforthesuperuser
Firstdatablock=0
Maximumfilesystemblocks=540016640
160blockgroups
16384blockspergroup,16384fragmentspergroup
2040inodespergroup
Superblockbackupsstoredonblocks:
16384,49152,81920,114688,147456,409600,442368,802816,1327104,
2048000
Writinginodetables:done
Creatingjournal(32768blocks):done
Writingsuperblocksandfilesystemaccountinginformation:done
Thisfilesystemwillbeautomaticallycheckedevery30mountsor
180days,whichevercomesfirst.Usetune2fs-cor-itooverride.</pre><p>4)使用dumpe2fs命令查询Inode和Block的大小：</p><pre class="brush:cpp;toolbar:false">[root@techW~]#dumpe2fs/dev/sdb2|grep"Inodesize"
dumpe2fs1.41.12(17-May-2010)
Inodesize:2048###大小更改成功
[root@techW~]#
s/dev/sdb2|grep"Blocksize"
dumpe2fs1.41.12(17-May-2010)
Blocksize:2048###大小更改成功</pre>