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LVM是逻辑盘卷管理（Logical Volume Manager）的简称，它是Linux环境下对磁盘分区进行管理的一种机制，LVM是建立在硬盘和分区之上的一个逻辑层，从而提高磁盘分区管理的灵活性。接下来通过实验来详细了解LVM的使用。
Linux入门教程：使用LVM逻辑卷管理器管理灵活存储 http://www.linuxidc.com/Linux/2014-07/104443.htm
CentOS 6.3下配置LVM（逻辑卷管理） http://www.linuxidc.com/Linux/2014-06/103839.htm
Linux LVM简明教程 http://www.linuxidc.com/Linux/2014-06/103390.htm
Linux的LVM(Logical Volume Manager) 学习笔记 http://www.linuxidc.com/Linux/2014-05/101880.htm
RHCE认证笔记：LVM实验 http://www.linuxidc.com/Linux/2014-04/99685.htm
Linux系统管理之LVM案例 http://www.linuxidc.com/Linux/2014-02/96987.htm
1.实验环境准备.添加一块未使用过的磁盘/dev/sdb,使用fdisk从其中分出两个5G的分区,并且将其分区类型该为8e
[root@localhost ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 21.5 GB, 21474836480 bytes
255 heads, 63 sectors/track, 2610 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0f199ec4
Device Boot Start End Blocks Id System
/dev/sdb1 1 654 5253223+ 8e Linux LVM
/dev/sdb2 655 1308 5253255 8e Linux LVM
2.创建物理卷:
[root@localhost ~]# pvcreate /dev/sdb1
Physical volume “/dev/sdb1” successfully created
[root@localhost ~]# pvcreate /dev/sdb2
dev_is_mpath: failed to get device for 8:18
Physical volume “/dev/sdb2” successfully created
[root@localhost ~]# pvscan
PV /dev/sda2 VG vg0 lvm2 [59.99 GiB / 7.99 GiB free]
PV /dev/sdb1 lvm2 [5.01 GiB]
PV /dev/sdb2 lvm2 [5.01 GiB]
Total: 3 [70.01 GiB] / in use: 1 [59.99 GiB] / in no VG: 2 [10.02 GiB]
3.在物理卷的基础上创建卷组,将/dev/sdb1加入卷组
[root@localhost ~]# vgcreate test /dev/sdb1
Volume group “test” successfully create
[root@localhost ~]# vgscan #可以看到卷组test已经创建成功
Reading all physical volumes. This may take a while…
Found volume group “test” using metadata type lvm2
Found volume group “vg0” using metadata type lvm2
4.在卷组test中创建一个大小为4G的逻辑卷test1
[root@localhost ~]# lvcreate -L 4G -n test1 test
Logical volume “test1” created
[root@localhost ~]# lvscan
ACTIVE ‘/dev/test/test1’ [4.00 GiB] inherit #test1已经创建成功
ACTIVE ‘/dev/vg0/root’ [20.00 GiB] inherit
ACTIVE ‘/dev/vg0/swap’ [2.00 GiB] inherit
ACTIVE ‘/dev/vg0/usr’ [10.00 GiB] inherit
ACTIVE ‘/dev/vg0/var’ [20.00 GiB] inherit
5.接下来就可以按照普通分区,对test1进行格式化,并且挂载使用了
[root@localhost ~]# mkfs.ext4 /dev/test/test1
mke2fs 1.41.12 (17-May-2010)
……
This filesystem will be automatically checked every 34 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
[root@localhost ~]# mkdir /test
[root@localhost ~]# mount /dev/test/test1 /test/
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-root 20G 428M 19G 3% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/sda1 194M 30M 155M 16% /boot
/dev/mapper/vg0-usr 9.9G 2.3G 7.2G 24% /usr
/dev/mapper/vg0-var 20G 361M 19G 2% /var
/dev/mapper/test-test1 4.0G 136M 3.7G 4% /test #逻辑卷成功创建
6.在/test下放入一个文件,测试可否使用
[root@localhost test]# echo “lv test” >a.txt
[root@localhost test]# cat a.txt
lv test
更多详情见请继续阅读下一页的精彩内容： http://www.linuxidc.com/Linux/2014-08/105381p2.htm
7.当我们使用完一段时间后,可能4G的空间不够用了,这种时候,我们可以对test1进行扩展.LVM的灵活性就展现出来了.例如我们想扩展到7G,但是经过查看,卷组中的空间已经不够使用,需要先对卷组进行扩展
[root@localhost test]# vgs test
VG #PV #LV #SN Attr VSize VFree
test 1 1 0 wz–n- 5.01g 1.01g
[root@localhost test]# vgextend test /dev/sdb2
Volume group “test” successfully extended
[root@localhost test]# vgs test
VG #PV #LV #SN Attr VSize VFree
test 2 1 0 wz–n- 10.02g 6.02g
8.扩展逻辑卷test1(首先扩展物理边界,再扩展文件系统边界)
[root@localhost test]# vgextend test /dev/sdb2
Volume group “test” successfully extended
[root@localhost test]# vgs test
VG #PV #LV #SN Attr VSize VFree
test 2 1 0 wz–n- 10.02g 6.02g
[root@localhost test]# lvextend -L 7G /dev/test/test1 #扩展物理边界
Extending logical volume test1 to 7.00 GiB
Logical volume test1 successfully resized
[root@localhost test]# resize2fs /dev/test/test1 #扩展文件系统边界
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/test/test1 is mounted on /test; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/test/test1 to 1835008 (4k) blocks.
The filesystem on /dev/test/test1 is now 1835008 blocks long.
[root@localhost test]# df -h #test1成功扩展到7G大小
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-root 20G 428M 19G 3% /
tmpfs 246M 0 246M 0% /dev/shm
/dev/sda1 194M 30M 155M 16% /boot
/dev/mapper/vg0-usr 9.9G 2.3G 7.2G 24% /usr
/dev/mapper/vg0-var 20G 361M 19G 2% /var
/dev/mapper/test-test1 6.9G 137M 6.5G 3% /test
9.对测试后的test1访问,查看文件是否被破坏
[root@localhost test]# cat a.txt #文件未被破坏
lv test
10.快照卷创建(用于文件系统备份等场景使用)
[root@localhost test]# lvcreate -n snap-test1 -L 2G -s /dev/test/test1 -p r
Logical volume “snap-test1” created
[root@localhost test]# mkdir /test.bak
[root@localhost test]# mount /dev/test/snap-test1 /test.bak/
mount: block device /dev/mapper/test-snap–test1 is write-protected, mounting read-only
11.查看test1及其快照卷的文件列表及a.txt的文件内容
[root@localhost /]# ls /test
a.txt lost+found
[root@localhost /]# ls /test.bak/
a.txt lost+found
[root@localhost test]# cat /test/a.txt /test.bak/a.txt
lv test
lv test
12.修改test1中的文件,查看在其快照卷中是否发生了改动
[root@localhost test]# echo “This is a new line” >>/test/a.txt
[root@localhost test]# cat /test/a.txt
lv test
This is a new line
[root@localhost test]# cat /test.bak/a.txt #快照卷的文件内容未发生改变
lv test
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