LVM介绍及相关操作

一、逻辑卷管理器介绍

逻辑卷管理器（英语：Logical Volume Manager，缩写为LVM），又译为逻辑卷宗管理器、逻辑扇区管理器、逻辑磁盘管理器，是Linux核心所提供的逻辑卷管理（Logical volume management）功能。它在硬盘的硬盘分区之上，又创建一个逻辑层，以方便系统管理硬盘分割系统。

最先由IBM开发，在AIX系统上实现，OS/2 操作系统与 HP-UX也支持这个功能。在1998年，Heinz Mauelshagen 根据在 HP-UX 上的逻辑卷管理器，写作出第一个 Linux 版本的逻辑卷管理器。

LVM基本术语：

• PV：物理卷，PV处于LVM系统最低层，它可以是整个硬盘，或者与磁盘分区具有相同功能的设备（如RAID），但和基本的物理存储介质相比较，多了与LVM相关管理参数
• VG：卷组，创建在PV之上，由一个或多个PV组成，可以在VG上创建一个或多个“LVM分区”（逻辑卷），功能类似非LVM系统的物理硬盘
• LV：逻辑卷，从VG中分割出的一块空间，创建之后其大小可以伸缩，在LV上可以创建文件系统（如/var,/home）
• PE：物理区域，每一个PV被划分为基本单元（也被称为PE），具有唯一编号的PE是可以被LVM寻址的最小存储单元，默认为4MB

LVM用于以下目的：

• 创建多个物理卷或整个硬盘的单个逻辑卷（有点类似于RAID 0，但更类似于JBOD），从而可以动态调整卷大小。
• 通过结合热插拔，允许添加和更换磁盘而不会造成停机或服务中断，从而管理大型硬盘场。
• 在小型系统（例如台式机）上，LVM不必在安装时估计分区可能需要多大，而是可以根据需要轻松调整文件系统的大小。
• 通过对逻辑卷进行快照来执行一致的备份。
• 使用一个密码加密多个物理分区。

LVM可被视为硬盘和分区之上的薄软件层，它创建了连续性和易用性的抽象，用于管理硬盘驱动器的更换，重新分区和备份。

二、逻辑卷管理器操作

1、LVM进行准备
#添加一块新硬盘/dev/sdb
[root@localhost ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0   20G  0 disk
sr0              11:0    1 1024M  0 rom  

#对新建硬盘/dev/sdb进行分区
[root@localhost ~]# fdisk /dev/sdb
Welcome to fdisk (util-linux 2.23.2).

Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xd1c551dc.

Command (m for help): n
Partition type:
   p   primary (0 primary, 0 extended, 4 free)
   e   extended
Select (default p): p
Partition number (1-4, default 1): 1
First sector (2048-41943039, default 2048): 2048
Last sector, +sectors or +size{K,M,G} (2048-41943039, default 41943039): +3G
Partition 1 of type Linux and of size 3 GiB is set

Command (m for help): n
Partition type:
   p   primary (1 primary, 0 extended, 3 free)
   e   extended
Select (default p): p
Partition number (2-4, default 2):
First sector (6293504-41943039, default 6293504):
Using default value 6293504
Last sector, +sectors or +size{K,M,G} (6293504-41943039, default 41943039): +4G
Partition 2 of type Linux and of size 4 GiB is set

Command (m for help): n
Partition type:
   p   primary (2 primary, 0 extended, 2 free)
   e   extended
Select (default p): p
Partition number (3,4, default 3):
First sector (14682112-41943039, default 14682112):
Using default value 14682112
Last sector, +sectors or +size{K,M,G} (14682112-41943039, default 41943039): +2G
Partition 3 of type Linux and of size 2 GiB is set

#对新建的三个主分区更改硬盘属性为“Linux LVM”（代码：8e）
Command (m for help): t
Partition number (1-3, default 3):
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): t
Partition number (1-3, default 3): 1
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): t
Partition number (1-3, default 3): 2
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'

Command (m for help): w
The partition table has been altered!

Calling ioctl() to re-read partition table.
Syncing disks.

#查看新硬盘的分区，及因硬盘属性
[root@localhost ~]# lsblk
NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda               8:0    0   20G  0 disk
├─sda1            8:1    0    1G  0 part /boot
└─sda2            8:2    0   19G  0 part
  ├─centos-root 253:0    0   17G  0 lvm  /
  └─centos-swap 253:1    0    2G  0 lvm  [SWAP]
sdb               8:16   0   20G  0 disk
├─sdb1            8:17   0    3G  0 part
├─sdb2            8:18   0    4G  0 part
└─sdb3            8:19   0    2G  0 part
sr0              11:0    1 1024M  0 rom
[root@localhost ~]# fdisk -l /dev/sdb

Disk /dev/sdb: 21.5 GB, 21474836480 bytes, 41943040 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0xd1c551dc

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1            2048     6293503     3145728   8e  Linux LVM
/dev/sdb2         6293504    14682111     4194304   8e  Linux LVM
/dev/sdb3        14682112    18876415     2097152   8e  Linux LVM

2、创建LVM
#对三个主分区进行PV（物理卷）创建
[root@localhost ~]# pvcreate /dev/sdb1
  Physical volume "/dev/sdb1" successfully created.
[root@localhost ~]# pvcreate /dev/sdb2
  Physical volume "/dev/sdb2" successfully created.
[root@localhost ~]# pvcreate /dev/sdb3
  Physical volume "/dev/sdb3" successfully created.

#查看三个主分区是否存在PV
[root@localhost ~]# pvs
  PV         VG     Fmt  Attr PSize   PFree
  /dev/sda2  centos lvm2 a--  <19.00g    0
  /dev/sdb1         lvm2 ---    3.00g 3.00g
  /dev/sdb2         lvm2 ---    4.00g 4.00g
  /dev/sdb3         lvm2 ---    2.00g 2.00g

#将三个PV添加到LVMtest的VG（卷组）中，并设置PE（物理区域）的大小为12M
[root@localhost ~]# vgcreate -s 12M LVMtest /dev/sdb{1..3}
  Volume group "LVMtest" successfully created

#查看LVMtest这个VG是否存在。
[root@localhost ~]# vgs
  VG      #PV #LV #SN Attr   VSize   VFree
  LVMtest   3   0   0 wz--n-  <8.98g <8.98g
  centos    1   2   0 wz--n- <19.00g     0 

#创建大小为4G的LVMtest的逻辑分区
[root@localhost ~]# lvcreate -L 4G -n LVMtest LVMtest
  Rounding up size to full physical extent <4.01 GiB
  Logical volume "LVMtest" created.

#查看LVMtest这个逻辑分区是否存在
[root@localhost ~]# lvs
  LV      VG      Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  LVMtest LVMtest -wi-a-----  <4.01g
  root    centos  -wi-ao---- <17.00g
  swap    centos  -wi-ao----   2.00g                                                    

#格式化分区/dev/LVMtest/LVMtest，设置分区类型为ext4，并将其挂载至/data/目录下
[root@localhost ~]# mkfs.ext4 /dev/LVMtest/LVMtest
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=4096 (log=2)
Fragment size=4096 (log=2)
Stride=0 blocks, Stripe width=0 blocks
262944 inodes, 1050624 blocks
52531 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=1075838976
33 block groups
32768 blocks per group, 32768 fragments per group
7968 inodes per group
Superblock backups stored on blocks:
	32768, 98304, 163840, 229376, 294912, 819200, 884736

Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done 

[root@localhost ~]# partprobe  //在不重启机器的情况下系统能够重新读取分区
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
[root@localhost ~]# lsblk
NAME                MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                   8:0    0   20G  0 disk
├─sda1                8:1    0    1G  0 part /boot
└─sda2                8:2    0   19G  0 part
  ├─centos-root     253:0    0   17G  0 lvm  /
  └─centos-swap     253:1    0    2G  0 lvm  [SWAP]
sdb                   8:16   0   20G  0 disk
├─sdb1                8:17   0    3G  0 part
│ └─LVMtest-LVMtest 253:2    0    4G  0 lvm
├─sdb2                8:18   0    4G  0 part
│ └─LVMtest-LVMtest 253:2    0    4G  0 lvm
└─sdb3                8:19   0    2G  0 part
sr0                  11:0    1  4.2G  0 rom  /mnt
[root@localhost ~]# mkdir /data
[root@localhost ~]# mount /dev/LVMtest/LVMtest /data

#复制一定的数据用于后面的测试
[root@localhost ~]# cp -R /etc/pam.d/ /data/
[root@localhost ~]# ll -d /data/
drwxr-xr-x. 4 root root 4096 Dec 24 02:16 /data/
[root@localhost ~]# ll -dl /data/
drwxr-xr-x. 4 root root 4096 Dec 24 02:16 /data/
[root@localhost ~]# ll  /data/
total 20
drwx------. 2 root root 16384 Dec 24 02:15 lost+found
drwxr-xr-x. 2 root root  4096 Dec 24 02:16 pam.d

3、对LVM进行增加容量实验
#为LVMtest分区新增2G容量，并验证数据完整性
	1）扩展物理边界
	2）扩展逻辑边界
[root@localhost ~]# lvextend -L +2G /dev/LVMtest/LVMtest //扩展物理边界
  Rounding size to boundary between physical extents: 2.00 GiB.
  Size of logical volume LVMtest/LVMtest changed from <4.01 GiB (342 extents) to 6.01 GiB (513 extents).
  Logical volume LVMtest/LVMtest successfully resized.

[root@localhost ~]# resize2fs /dev/LVMtest/LVMtest	//扩展逻辑边界
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/LVMtest/LVMtest is mounted on /data; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/LVMtest/LVMtest is now 1575936 blocks long.

[root@localhost ~]# ls -l /data/
total 20
drwx------. 2 root root 16384 Dec 24 02:15 lost+found
drwxr-xr-x. 2 root root  4096 Dec 24 02:16 pam.d

4、对LVM进行缩减容量
#将LVMtest缩减至2G大小，并验证数据完整性（在生产环境中，不建议进行此操作！！！！！）
#在这里采用ext4的文件系统类型，
	1）先卸载物理文件系统
	2）对文件系统进行强制检测和修复
	3）缩减逻辑边界
	4）缩减物理边界
	5）重新挂载LVM分区
[root@localhost ~]# umount /dev/LVMtest/LVMtest/

[root@localhost ~]# e2fsck -f /dev/LVMtest/LVMtest //对文件系统进行强制检测和修复
e2fsck 1.42.9 (28-Dec-2013)
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/LVMtest/LVMtest: 43/390432 files (0.0% non-contiguous), 61412/1575936 blocks

[root@localhost ~]# resize2fs /dev/LVMtest/LVMtest 2G //缩减逻辑边界为2G大小
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/LVMtest/LVMtest to 524288 (4k) blocks.
The filesystem on /dev/LVMtest/LVMtest is now 524288 blocks long.

[root@localhost ~]# lvreduce -L 2G /dev/LVMtest/LVMtest //缩减物理边界为2G大小
  Rounding size to boundary between physical extents: 2.00 GiB.
  WARNING: Reducing active logical volume to 2.00 GiB.
  THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce LVMtest/LVMtest? [y/n]: y
  Size of logical volume LVMtest/LVMtest changed from 6.01 GiB (513 extents) to 2.00 GiB (171 extents).
  Logical volume LVMtest/LVMtest successfully resized.

[root@localhost ~]# mount /dev/LVMtest/LVMtest /data //重新挂载LVM分区

#检查LVM分区大小
[root@localhost ~]# lsblk
NAME                MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
sda                   8:0    0   20G  0 disk
├─sda1                8:1    0    1G  0 part /boot
└─sda2                8:2    0   19G  0 part
  ├─centos-root     253:0    0   17G  0 lvm  /
  └─centos-swap     253:1    0    2G  0 lvm  [SWAP]
sdb                   8:16   0   20G  0 disk
├─sdb1                8:17   0    3G  0 part
├─sdb2                8:18   0    4G  0 part
│ └─LVMtest-LVMtest 253:2    0    2G  0 lvm  /data
└─sdb3                8:19   0    2G  0 part
sr0                  11:0    1  4.2G  0 rom  /mnt

#检查数据完整性
[root@localhost ~]# ll /data/
total 20
drwx------. 2 root root 16384 Dec 24 02:15 lost+found
drwxr-xr-x. 2 root root  4096 Dec 24 02:16 pam.d

5、删除LVM案例
#卸载LVM的分区
[root@localhost ~]# umount /data/

#删除在LVMtest上的LVM分区
[root@localhost ~]# lvremove /dev/LVMtest/LVMtest
Do you really want to remove active logical volume LVMtest/LVMtest? [y/n]: y
  Logical volume "LVMtest" successfully removed

#删除在LVMtest上的VG（卷组）
[root@localhost ~]# vgremove LVMtest
  Volume group "LVMtest" successfully removed

#删除在硬盘分区的PV
[root@localhost ~]# pvremove /dev/sdb1
  Labels on physical volume "/dev/sdb1" successfully wiped.
[root@localhost ~]# pvremove /dev/sdb2
  Labels on physical volume "/dev/sdb2" successfully wiped.
[root@localhost ~]# pvremove /dev/sdb3
  Labels on physical volume "/dev/sdb3" successfully wiped.

[root@localhost ~]# pvs
  PV         VG     Fmt  Attr PSize   PFree
  /dev/sda2  centos lvm2 a--  <19.00g    0 

[root@localhost ~]# vgs
  VG     #PV #LV #SN Attr   VSize   VFree
  centos   1   2   0 wz--n- <19.00g    0 

[root@localhost ~]# lvs
  LV   VG     Attr       LSize   Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  root centos -wi-ao---- <17.00g
  swap centos -wi-ao----   2.00g