逻辑卷管理器，通过将另外一个硬盘上的分区加到已有文件系统，来动态地向已有文件系统添加空间的方法。
逻辑卷管理的核心是处理安装在系统上的硬盘分区。在逻辑卷管理的世界里，硬盘称作物理卷（Physical Volume,PV).每个物理卷都会映射到硬盘上创建的某一个物理分区。
多个物理卷元素集中在一起可以组成一个卷组（Volume Group,VG)。逻辑卷管理系统会把卷组当做物理硬盘一样对待，但事实上卷组可能是由分布多个物理硬盘上的多个物理分区组成的。卷组提供了一个创建逻辑分区的平台，而这些逻辑分区事实上包含了文件系统。
整个结构中的最后一层是逻辑卷（Logic Volume,LV)。逻辑卷为Linux提供了创建文件系统的分区环境，作用类似于到目前为止我们一直在探讨的Linux中的物理硬盘。Linux系统将逻辑卷当做物理分区对待。可以使用任意一种标准Linux文件系统来格式化逻辑卷，然后再将它在某个挂载点添加进入Linux虚拟目录中。
一.创建LINUX LVM
1、定义物理卷
[root@TP-CW-TS-DB-01 ~]# fdisk /dev/sdb
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): t
Partition number (1-6): 8e
Value out of range.
Partition number (1-6): quit
Partition number (1-6): ^C
[root@TP-CW-TS-DB-01 ~]# fdisk /dev/sdb
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): t
Partition number (1-6): 1
Hex code (type L to list codes): 8e
Changed system type of partition 1 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-6): 2
Hex code (type L to list codes): 8e
Changed system type of partition 2 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-6): 3
Hex code (type L to list codes): 8e
Changed system type of partition 3 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-6): 4
Hex code (type L to list codes): 8e
You cannot change a partition into an extended one or vice versa
Delete it first.
Command (m for help): t
Partition number (1-6): 5
Hex code (type L to list codes): 8e
Changed system type of partition 5 to 8e (Linux LVM)
Command (m for help): t
Partition number (1-6): 6
Hex code (type L to list codes): 8e
Changed system type of partition 6 to 8e (Linux LVM)
Command (m for help): w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@TP-CW-TS-DB-01 ~]# fdisk /dev/sdb
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): p
Disk /dev/sdb: 300.0 GB, 300000000000 bytes
255 heads, 63 sectors/track, 36472 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: 0xc82dffc2
Device Boot Start End Blocks Id System
/dev/sdb1 1 30 240943+ 8e Linux LVM
/dev/sdb2 31 2642 20980890 8e Linux LVM
/dev/sdb3 2643 3948 10490445 8e Linux LVM
/dev/sdb4 3949 6560 20980890 5 Extended
/dev/sdb5 3949 5254 10490413+ 8e Linux LVM
/dev/sdb6 5255 6560 10490413+ 8e Linux LVM
用来sdb的6个分区转换成Linux LVM分区，8e分区类型表示这个分区将会被用做Linux LVM系统的一部分，而不是一个直接的文件系统，
2、创建PV
[root@TP-CW-TS-DB-01 ~]# pvcreate /dev/sdb5 Physical volume "/dev/sdb5" successfully created [root@TP-CW-TS-DB-01 ~]# pvcreate /dev/sdb6 Physical volume "/dev/sdb6" successfully created [root@TP-CW-TS-DB-01 ~]# pvs /dev/drbd0: open failed: Wrong medium type PV VG Fmt Attr PSize PFree /dev/sda2 VolGroup lvm2 a- 67.88g 0 /dev/sdb5 lvm2 a- 10.00g 10.00g /dev/sdb6 lvm2 a- 10.00g 10.00g
3.创建VGS
[root@TP-CW-TS-DB-01 ~]# vgcreate onlinevg /dev/sdb5
Volume group "onlinevg" successfully created
[root@TP-CW-TS-DB-01 ~]# vgcreate onlinevg /dev/sdb6
A volume group called onlinevg already exists.
[root@TP-CW-TS-DB-01 ~]# vgcreate onlinevg /dev/sdb{5,6}
Volume group "onlinevg" successfully created
[root@TP-CW-TS-DB-01 ~]# vgs
VG #PV #LV #SN Attr VSize VFree
VolGroup 1 3 0 wz--n- 67.88g 0
onlinevg 2 0 0 wz--n- 20.00g 20.00g
4、创建LV
[root@TP-CW-TS-DB-01 ~]# lvcreate -L 5G -n mylv onlinevg Logical volume "mylv" created [root@TP-CW-TS-DB-01 ~]# lvs LV VG Attr LSize Origin Snap% Move Log Copy% Convert lv_home VolGroup -wi-ao 17.81g lv_root VolGroup -wi-ao 32.36g lv_swap VolGroup -wi-ao 17.70g mylv onlinevg -wi-a- 5.00g
逻辑卷的设备文件：/dev/VG_NAME/LV_NAME
[root@TP-CW-TS-DB-01 ~]# ls /dev/onlinevg/mylv /dev/onlinevg/mylv [root@TP-CW-TS-DB-01 ~]# ls -l /dev/onlinevg/mylv lrwxrwxrwx. 1 root root 7 Oct 12 16:21 /dev/onlinevg/mylv -> ../dm-3
5、格式化LV
mke2fs -t ext4 /dev/onlinevg/mylv
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
327680 inodes, 1310720 blocks
65536 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 32 mounts or
180 days, whichever comes first. Use tune2fs -c or -i to override.
6、挂载分区
[root@TP-CW-TS-DB-01 ~]# mount /dev/onlinevg/mylv /mnt/
[root@TP-CW-TS-DB-01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
32G 3.7G 27G 13% /
tmpfs 7.8G 0 7.8G 0% /dev/shm
/dev/sda1 485M 49M 411M 11% /boot
/dev/mapper/VolGroup-lv_home
18G 172M 17G 2% /home
/dev/mapper/onlinevg-mylv
5.0G 138M 4.6G 3% /mnt
二、扩展VG
1、首先在创建一个PV
[root@TP-CW-TS-DB-01 mnt]# pvcreate /dev/sdb3 Physical volume "/dev/sdb3" successfully created
2、通过vgcreatend命令扩展VG
[root@TP-CW-TS-DB-01 mnt]# vgs VG #PV #LV #SN Attr VSize VFree VolGroup 1 3 0 wz--n- 67.88g 0 onlinevg 2 1 0 wz--n- 20.00g 15.00g [root@TP-CW-TS-DB-01 mnt]# vgextend onlinevg /dev/sdb sdb sdb1 sdb2 sdb3 sdb4 sdb5 sdb6 [root@TP-CW-TS-DB-01 mnt]# vgextend onlinevg /dev/sdb3 Volume group "onlinevg" successfully extended [root@TP-CW-TS-DB-01 mnt]# vgs VG #PV #LV #SN Attr VSize VFree VolGroup 1 3 0 wz--n- 67.88g 0 onlinevg 3 1 0 wz--n- 30.00g 25.00g
通过命令查看onlinevg扩展到了30G
[root@TP-CW-TS-DB-01 mnt]# pvs PV VG Fmt Attr PSize PFree /dev/sda2 VolGroup lvm2 a- 67.88g 0 /dev/sdb3 onlinevg lvm2 a- 10.00g 10.00g /dev/sdb5 onlinevg lvm2 a- 10.00g 5.00g /dev/sdb6 onlinevg lvm2 a- 10.00g 10.00g
三、缩减VG
1、确定要移除的PV(/dev/sdb5)
2、利用pvmove将/dev/sdb5中的数据移到物理卷上
pvmove /dev/sdb5 /dev/sdb5:Mover:100.0%
3、从卷组中将缩减vg
[root@TP-CW-TS-DB-01 ~]# vgreduce onlinevg /dev/sdb5 Removed "/dev/sdb5" from volume group "onlinevg" [root@TP-CW-TS-DB-01 ~]# vgs VG #PV #LV #SN Attr VSize VFree VolGroup 1 3 0 wz--n- 67.88g 0 onlinevg 2 1 0 wz--n- 20.00g 15.00g
4、删除/dev/sdb5
[root@TP-CW-TS-DB-01 ~]# pvremove /dev/sdb5 Labels on physical volume "/dev/sdb5" successfully wiped
四、扩展逻辑卷
1、扩展物理边界
[root@TP-CW-TS-DB-01 ~]# lvextend -L +3G /dev/onlinevg/mylv Extending logical volume mylv to 8.00 GiB Logical volume mylv successfully resized
注意：这个是候文件系统挂载的/mnt大小不会有任何变化
2、扩展逻辑边界
[root@TP-CW-TS-DB-01 ~]# resize2fs /dev/onlinevg/mylv
resize2fs 1.41.12 (17-May-2010)
Filesystem at /dev/onlinevg/mylv is mounted on /mnt; on-line resizing required
old desc_blocks = 1, new_desc_blocks = 1
Performing an on-line resize of /dev/onlinevg/mylv to 2097152 (4k) blocks.
The filesystem on /dev/onlinevg/mylv is now 2097152 blocks long.
[root@TP-CW-TS-DB-01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
32G 3.7G 27G 13% /
tmpfs 7.8G 0 7.8G 0% /dev/shm
/dev/sda1 485M 49M 411M 11% /boot
/dev/mapper/VolGroup-lv_home
18G 172M 17G 2% /home
/dev/mapper/onlinevg-mylv
7.9G 140M 7.4G 2% /mnt
五、缩减逻辑卷
1、卸载并强行检测文件系统：
umount /mnt
[root@TP-CW-TS-DB-01 ~]# e2fsck -f /dev/onlinevg/mylv e2fsck 1.41.12 (17-May-2010) Pass 1: Checking inodes, blocks, and sizes Pass 2: Checking directory structure Pass 3: Checking directory connectivity Pass 4: Checking reference counts Pass 5: Checking group summary information /dev/onlinevg/mylv: 12/524288 files (0.0% non-contiguous), 68564/2097152 blocks
2、缩减逻辑边界
[root@TP-CW-TS-DB-01 ~]# resize2fs /dev/onlinevg/mylv 3G resize2fs 1.41.12 (17-May-2010) Resizing the filesystem on /dev/onlinevg/mylv to 786432 (4k) blocks. The filesystem on /dev/onlinevg/mylv is now 786432 blocks long.
3、缩减物理边界
[root@TP-CW-TS-DB-01 ~]# lvreduce -L 3G /dev/onlinevg/mylv
WARNING: Reducing active logical volume to 3.00 GiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce mylv? [y/n]: y
Reducing logical volume mylv to 3.00 GiB
Logical volume mylv successfully resized
[root@TP-CW-TS-DB-01 ~]# mount /dev/onlinevg/mylv /mnt
[root@TP-CW-TS-DB-01 ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
32G 3.7G 27G 13% /
tmpfs 7.8G 0 7.8G 0% /dev/shm
/dev/sda1 485M 49M 411M 11% /boot
/dev/mapper/VolGroup-lv_home
18G 172M 17G 2% /home
/dev/mapper/onlinevg-mylv
3.0G 136M 2.7G 5% /mnt
六、创建快照卷
lvcreate
-s:快照卷：
-p r:只读
-n：定义快照
[root@TP-CW-TS-DB-01 dev]# lvcreate -L 100M -s -p r -n mylv-snap /dev/onlinevg/mylv
[root@TP-CW-TS-DB-01 dev]# mount -o ro /dev/onlinevg/mylv-snap /media
[root@TP-CW-TS-DB-01 dev]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
32G 3.7G 27G 13% /
tmpfs 7.8G 0 7.8G 0% /dev/shm
/dev/sda1 485M 49M 411M 11% /boot
/dev/mapper/VolGroup-lv_home
18G 172M 17G 2% /home
/dev/mapper/onlinevg-mylv
3.0G 136M 2.7G 5% /mnt
/dev/mapper/onlinevg-mylv--snap
3.0G 136M 2.7G 5% /media