LVM可以使硬盘无限扩容：
PV(physical volume)：物理卷在逻辑卷管理系统最底层，可为整个物理硬盘或实际物理硬盘上的分区。
VG(volume group)：卷组建立在物理卷上，一卷组中至少要包括一物理卷，卷组建立后可动态的添加卷到卷组中，一个逻辑卷管理系统工程中可有多个卷组。
LV(logical volume)：逻辑卷建立在卷组基础上，卷组中未分配空间可用于建立新的逻辑卷，逻辑卷建立后可以动态扩展和缩小空间。
PE(physical extent)：物理区域是物理卷中可用于分配的最小存储单元，物理区域大小在建立卷组时指定，一旦确定不能更改，同一卷组所有物理卷的物理区域大小需一致，新的pv加入到vg后，pe的大小自动更改为vg中定义的pe大小。
LE(logical extent)：逻辑区域是逻辑卷中可用于分配的最小存储单元，逻辑区域的大小取决于逻辑卷所在卷组中的物理区域的大小。
卷组描述区域：卷组描述区域存在于每个物理卷中，用于描述物理卷本身、物理卷所属卷组、卷组中逻辑卷、逻辑卷中物理区域的分配等所有信息，它是在使用pvcreate建立物理卷时建立的。
LVM原理图：
还原当前的环境：
[root@localhost ~]# umount /mnt/ 解除挂载
[root@localhost ~]# vim /etc/fstab 删除开机自动挂载
[root@localhost ~]# cat /etc/fstab 查看文件内容已经被删除
[root@localhost ~]# fdisk /dev/vdb 删除分区
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.
Command (m for help): d 删除分区
Selected partition 1
Partition 1 is deleted
Command (m for help): wq
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe 同步
[root@localhost ~]# fdisk -l 查看硬件信息
Disk /dev/vda: 10.7 GB, 10737418240 bytes, 20971520 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: 0x00013f3e
Device Boot Start End Blocks Id System
/dev/vda1 * 2048 20970332 10484142+ 83 Linux
Disk /dev/vdb: 10.7 GB, 10737418240 bytes, 20971520 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: 0x54f9eab8
Device Boot Start End Blocks Id System内容简单，演示一下过程图：
解除挂载删除分区：
查看硬件信息：
LVM逻辑卷的管理：
打开两个shell，同时连接server虚拟机将其中一台A进行监控,在另外一台B查看命令效果
A：
[root@localhost ~]# watch -n 1 'pvs;vgs;lvs;df -h /mnt'B：
[root@localhost ~]# fdisk /dev/vdb 建立三个1G分区并更改类型为8e
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): wq
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe 同步
[root@localhost ~]# pvcreate /dev/vdb1
Can't open /dev/vdb1 exclusively. Mounted filesystem?报错意思vdb1已经被挂载
[root@localhost ~]# df 查看时候已经被挂载
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3804408 6669492 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 80 484852 1% /dev/shm
tmpfs 484932 12784 472148 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
/dev/vdb1 1038336 53416 984920 6% /mnt
[root@localhost ~]# umount /mnt/ 解除挂载
[root@localhost ~]# pvcreate /dev/vdb1 将分区做成物理卷
WARNING: xfs signature detected on /dev/vdb1 at offset 0. Wipe it? [y/n] y
Wiping xfs signature on /dev/vdb1.
Physical volume "/dev/vdb1" successfully created
[root@localhost ~]# vgcreate vg0 /dev/vdb1 创建卷组
Volume group "vg0" successfully created
[root@localhost ~]# lvcreate -L 300M -n lv0 vg0 创建逻辑卷并指定逻辑卷的大小为300M
Logical volume "lv0" created
[root@localhost ~]# mkfs.xfs /dev/vg0/lv0 将逻辑卷格式化
meta-data=/dev/vg0/lv0 isize=256 agcount=4, agsize=19200 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=76800, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal log bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
[root@localhost ~]# mount /dev/vg0/lv0 /mnt/ linux下的文件系统需要挂载才可以使用，将逻辑卷挂载
[root@localhost ~]# df
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3804420 6669480 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 80 484852 1% /dev/shm
tmpfs 484932 12788 472144 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
/dev/mapper/vg0-lv0 303788 15520 288268 6% /mnt
[root@localhost ~]# ll /dev/vg0/lv0 两个文件内容一样
lrwxrwxrwx. 1 root root 7 May 4 22:54 /dev/vg0/lv0 -> ../dm-0
[root@localhost ~]# ll /dev/mapper/vg0-lv0 lv
ls: cannot access lv: No such file or directory
lrwxrwxrwx. 1 root root 7 May 4 22:54 /dev/mapper/vg0-lv0 -> ../dm-0B虚拟机中操作，A虚拟机中操作：
建立分区同步建立物理卷：
建立物理卷失败是由于没有解除挂载：
格式化进行挂载
我们可以看一下A虚拟机监控的最终情况：
如下图所示已经建立了物理卷，物理卷组，逻辑卷。
LVM逻辑卷的扩容：
[root@localhost ~]# df 查看挂载
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3804380 6669520 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 80 484852 1% /dev/shm
tmpfs 484932 12816 472116 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
/dev/mapper/vg0-lv0 303788 15520 288268 6% /mnt
[root@localhost ~]# lvextend -L 500M /dev/vg0/lv0 扩展，但是文件系统不会更改
Extending logical volume lv0 to 500.00 MiB
Logical volume lv0 successfully resized
[root@localhost ~]# xfs_growfs /dev/vg0/lv0 将文件系统扩展
meta-data=/dev/mapper/vg0-lv0 isize=256 agcount=4, agsize=19200 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=76800, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 76800 to 128000
[root@localhost ~]# pvcreate /dev/vdb2 将分区做成物理卷
Physical volume "/dev/vdb2" successfully created
[root@localhost ~]# vgextend vg0 /dev/vdb2 创建卷组
Volume group "vg0" successfully extended
[root@localhost ~]# lvextend -L 1500M /dev/vg0/lv0 因为1.5G不够我们扩容，所以要另外增加vdb2，扩容。
Extending logical volume lv0 to 1.46 GiB
Logical volume lv0 successfully resized
[root@localhost ~]# xfs_growfs /dev/vg0/lv0 从监控来看文件系统依旧没有扩展所以需要这个命令扩展文件系统
meta-data=/dev/mapper/vg0-lv0 isize=256 agcount=7, agsize=19200 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0
data = bsize=4096 blocks=128000, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
data blocks changed from 128000 to 384000B虚拟机，对逻辑卷和文件系统进行扩容：
不够扩容了，所以需要建立物理卷2来进行扩容。
A虚拟机的监控来看效果已经扩容成功：
xfs文件系统不支持缩容操作。
LVM逻辑卷的扩容（逻辑卷格式为ext4）
[root@localhost ~]# umount /mnt/ 解除挂载
[root@localhost ~]# mkfs.ext4 /dev/vg0/lv0 将逻辑卷格式化成ext4格式
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
96000 inodes, 384000 blocks
19200 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=394264576
12 block groups
32768 blocks per group, 32768 fragments per group
8000 inodes per group
Superblock backups stored on blocks:
32768, 98304, 163840, 229376, 294912
Allocating group tables: done
Writing inode tables: done
Creating journal (8192 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# mount /dev/vg0/lv0 /mnt 将逻辑卷挂载到/mnt下
[root@localhost ~]# ls /mnt 查看/mnt
lost+found
[root@localhost ~]# lvextend -L 1800M /dev/vg0/lv0 扩展逻辑卷
Extending logical volume lv0 to 1.76 GiB
Logical volume lv0 successfully resized
[root@localhost ~]# resize2fs /dev/vg0/lv0 更新逻辑卷信息
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/vg0/lv0 is mounted on /mnt; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 1
The filesystem on /dev/vg0/lv0 is now 460800 blocks long.B虚拟机进行扩容操作，A虚拟机查看效果：
1，格式化成ext4格式
2，将文件系统和逻辑卷均进行扩容：
A虚拟机查看效果，已经成功扩容：；
LVM缩容操作：（很少使用，xfs文件系统不支持，ext文件系统支持）
[root@localhost ~]# umount /mnt/ 卸载
[root@localhost ~]# e2fsck -f /dev/vg0/lv0 检查是否有错误
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/vg0/lv0: 11/120000 files (9.1% non-contiguous), 16862/460800 blocks
[root@localhost ~]# resize2fs /dev/vg0/lv0 1000M 赋予新的容量
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/vg0/lv0 to 256000 (4k) blocks.
The filesystem on /dev/vg0/lv0 is now 256000 blocks long.
[root@localhost ~]# mount /dev/vg0/lv0 /mnt 挂载
[root@localhost ~]# lvreduce -L 1000M /dev/vg0/lv0 更新逻辑卷信息
WARNING: Reducing active and open logical volume to 1000.00 MiB
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv0? [y/n]: y
Reducing logical volume lv0 to 1000.00 MiB
Logical volume lv0 successfully resized在B虚拟机操作，A虚拟机进行监控：
B进行缩容：
A进行查看已经缩容成功：
如何缩减VG：
[root@localhost ~]# pvmove /dev/vdb1 /dev/vdb2 将vdb1移到闲置的vdb2中
/dev/vdb1: Moved: 4.8%
/dev/vdb1: Moved: 78.8%
/dev/vdb1: Moved: 100.0%
[root@localhost ~]# vgreduce vg0 /dev/vdb1 从vg中移除vdb1
Removed "/dev/vdb1" from volume group "vg0"
[root@localhost ~]# pvremove /dev/vdb1 删除/vdb1
Labels on physical volume "/dev/vdb1" successfully wiped
pvremove [选项] [参数]
pvremove指令用于删除一个存在的物理卷
主要参数：
-d 调试模式
-f 强制删除
-y 对提问回答“yes”
[root@localhost ~]# pvs 查看设备容量
PV VG Fmt Attr PSize PFree
/dev/vdb2 vg0 lvm2 a-- 1020.00m 20.00m
[root@localhost ~]# df -H 查看设备信息
Filesystem Size Used Avail Use% Mounted on
/dev/vda1 11G 3.9G 6.9G 37% /
devtmpfs 481M 0 481M 0% /dev
tmpfs 497M 82k 497M 1% /dev/shm
tmpfs 497M 14M 484M 3% /run
tmpfs 497M 0 497M 0% /sys/fs/cgroup
/dev/mapper/vg0-lv0 999M 3.9M 933M 1% /mntA虚拟机中监控到将/vdb1移到/vdb2中时：
B虚拟机中进行vg的缩减：
A虚拟机查看最后的vg缩减查看：
LVM的快照指令：
[root@localhost ~]# df 查看挂载
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/vda1 10473900 3808456 6665444 37% /
devtmpfs 469344 0 469344 0% /dev
tmpfs 484932 80 484852 1% /dev/shm
tmpfs 484932 12788 472144 3% /run
tmpfs 484932 0 484932 0% /sys/fs/cgroup
/dev/mapper/vg0-lv0 975128 3764 910288 1% /mnt
[root@localhost ~]# cd /mnt
[root@localhost mnt]# ls
lost+found
[root@localhost mnt]# touch westos{1..10} 建立文件
[root@localhost mnt]# ls
lost+found westos10 westos3 westos5 westos7 westos9
westos1 westos2 westos4 westos6 westos8
[root@localhost mnt]# rm -fr *
[root@localhost mnt]# ls
[root@localhost mnt]# touch westos{1..7}
[root@localhost mnt]# cd
[root@localhost ~]# umount /mnt/ 解除挂载
[root@localhost ~]# ls /mnt/
[root@localhost ~]# lvcreate -L 50M -n lv0backup -s /dev/vg0/lv0 拍照，-s代表拍照到指定路径，-n后面接照片名字，报错是因为大小不够
Rounding up size to full physical extent 52.00 MiB
Volume group "vg0" has insufficient free space (5 extents): 13 required.
[root@localhost ~]# pvcreate /dev/vdb1 将分区做成物理卷
Physical volume "/dev/vdb1" successfully created
[root@localhost ~]# vgextend vg0 /dev/vdb1 创建卷组
Volume group "vg0" successfully extended
[root@localhost ~]# lvcreate -L 50M -n lv0backup -s /dev/vg0/lv0拍照
Rounding up size to full physical extent 52.00 MiB
Logical volume "lv0backup" created
[root@localhost ~]# mount /dev/vg0/lv0backup /mnt/ 挂载
[root@localhost ~]# cd /mnt/
[root@localhost mnt]# ls
westos1 westos2 westos3 westos4 westos5 westos6 westos7
[root@localhost mnt]# rm -fr *
[root@localhost mnt]# ls
[root@localhost mnt]# cd
[root@localhost ~]# lvremove /dev/vg0/lv0backup 删除照片报错是因为没有解除挂载
Logical volume vg0/lv0backup contains a filesystem in use.
[root@localhost ~]# umount /mnt/ 解除挂载
[root@localhost ~]# lvremove /dev/vg0/lv0backup 删除照片成功
Do you really want to remove active logical volume lv0backup? [y/n]: y
Logical volume "lv0backup" successfully removed
[root@localhost ~]# lvcreate -L 50M -n lv0backup -s /dev/vg0/lv0拍照
Rounding up size to full physical extent 52.00 MiB
Logical volume "lv0backup" created
[root@localhost ~]# mount /dev/vg0/lv0backup /mnt/ 挂载
[root@localhost ~]# ls /mnt/ 查看文件文件还在证明我们仅仅删除了快照本来文件不受影响
westos1 westos2 westos3 westos4 westos5 westos6 westos7虚拟机的快照t同样可以借助监控，然后可以更好的进行快照命令的效果查看：
可以看到只剩下20M的可用空间：
首先在/mnt中建立七个文件为了让我们懂得快照的真实含义，读取的时候是读取本来的，写入时操作的是照片。
将/vdb1做成物理卷解决磁盘空间不够的问题，进行快照指令然后挂载查看就可以看到我们建立的七个文件。
A虚拟机监控看到的将/vdb1做成物理卷之后就解决了磁盘空间不够的问题，也就可以弄成快照。
删除照片重新做快照进行查看文件还在，就是证明有了快照本来文件不会受到影响。
彻底删除LVM，还原原来的分区：
[root@localhost ~]# umount /mnt/ 卸载
[root@localhost ~]# lvremove /dev/vg0/lv0backup 删除快照
Do you really want to remove active logical volume lv0backup? [y/n]: y
Logical volume "lv0backup" successfully removed
[root@localhost ~]# lvremove /dev/vg0/lv0 删除逻辑卷
Do you really want to remove active logical volume lv0? [y/n]: y
Logical volume "lv0" successfully removed
[root@localhost ~]# vgremove vg0 删除卷组
Volume group "vg0" successfully removed
[root@localhost ~]# pvremove /dev/vdb{1..2} 删除物理卷
Labels on physical volume "/dev/vdb1" successfully wiped
Labels on physical volume "/dev/vdb2" successfully wiped在B虚拟机操作：
分别卸载设备，删除快照，物理卷，物理卷组，逻辑卷，还原原本状态。
A虚拟机监控情况，发现已经还原到原来：
