Linux-LVM逻辑卷管理

一.LVM逻辑卷
LVM是一种基于内核的逻辑卷管理器，适用于管理大存储设备，并允许用户动态调整文件系统的大小。
需要了解的概念有
物理存储介质：指系统的物理存储设备：磁盘，如：/dev/hda、/dev/sda等
物理卷PV：是LVM逻辑存储块，物理卷与磁盘分区是逻辑对应关系。多个LVM物理卷可以合并或拆分，从而实现容量的扩容与缩减
卷组VG：是LVM逻辑概念上的磁盘设备，通过将单个或者多个物理卷组合成卷组。卷组的大小取决于物理卷的容量及个数
逻辑卷LV：逻辑卷就是LVM逻辑意义上的分区，可以指定从卷组中提取多少容量来创建逻辑卷，最后对逻辑卷挂载及使用
物理长度PE：将物理卷组合成卷组后，所划分的最小存储单位即逻辑意义上磁盘的最小存储单元。LVM中默认PE大小为4MB
逻辑块LE：逻辑卷LV也被划分为称为LE的基本单位，在同一个卷组中，LE的大小和PE是相同的，并且一一对应
二.LVM创建
1.新建磁盘并改变磁盘标签为8e

[root@localhost ~]# fdisk /dev/vdb
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 0x29d83a76.

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): 
First sector (2048-20971519, default 2048): 
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-20971519, default 20971519): +100M
Partition 1 of type Linux and of size 100 MiB 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 (206848-20971519, default 206848): 
Using default value 206848
Last sector, +sectors or +size{K,M,G} (206848-20971519, default 20971519): +500M
Partition 2 of type Linux and of size 500 MiB is set

Command (m for help): p

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: 0x29d83a76

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048      206847      102400   83  Linux
/dev/vdb2          206848     1230847      512000   83  Linux

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

Command (m for help): p

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: 0x29d83a76

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048      206847      102400   83  Linux
/dev/vdb2          206848     1230847      512000   8e  Linux LVM  ##更改成功

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

Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]# partprobe  ##同步磁盘分区

2.pv.vg.lv及其挂载的监控
watch -n 1 'pvs;echo ====;vgs;echo ====;lvs;echo ====;df -h /mnt ##监控pv vg lv 以及挂载情况
pvs ##查看物理卷
vgs ##查看逻辑卷组
lvs ##查看逻辑卷
由于未建立逻辑组逻辑卷所以此时监控到的逻辑组逻辑卷无数据

3.创建逻辑组逻辑卷
（1）物理卷
pvcreate /dev/vdb1 #把物理分区做成物理卷

（2）物理卷组
vgcreate vg0 /dev/vdb1 #制作一个物理卷组vg0

（3）逻辑卷
lvcreate -L 100M -n lv0 vg0 #在vg0这个组中建立出逻辑卷 -L 指定大小 -n 指定名字

4.逻辑卷lv0格式化及挂载，可以正常使用

[root@localhost ~]# mkfs.xfs /dev/vg0/lv0  ##格式化
meta-data=/dev/vg0/lv0           isize=256    agcount=4, agsize=6400 blks
         =                       sectsz=512   attr=2, projid32bit=1
         =                       crc=0
data     =                       bsize=4096   blocks=25600, 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 ~]# blkid  ##查看可用设备
/dev/vda1: UUID="9bf6b9f7-92ad-441b-848e-0257cbb883d1" TYPE="xfs" 
/dev/vdb2: UUID="82l7Ac-WkLd-1TpK-H18R-lHJL-5nUO-tcipdV" TYPE="LVM2_member" 
/dev/sr0: UUID="2016-10-19-18-32-06-00" LABEL="RHEL-7.3 Server.x86_64" TYPE="iso9660" PTTYPE="dos" 
/dev/mapper/vg0-lv0: UUID="4a6745d6-9657-451e-89c6-6a287dd2f310" TYPE="xfs"   ##/可用则格式化成功
[root@localhost ~]# mount /dev/vg0/lv0 /mnt  ##挂载在/mnt
[root@localhost ~]# df
Filesystem          1K-blocks    Used Available Use% Mounted on
/dev/vda1            10473900 3176344   7297556  31% /
devtmpfs               927060       0    927060   0% /dev
tmpfs                  942648     140    942508   1% /dev/shm
tmpfs                  942648   17072    925576   2% /run
tmpfs                  942648       0    942648   0% /sys/fs/cgroup
/dev/sr0              3704296 3704296         0 100% /run/media/root/RHEL-7.3 Server.x86_64
/dev/mapper/vg0-lv0     98988    5280     93708   6% /mnt  ##挂载成功

注意:/dev/mapper/vg0-lv0与/dev/vg0/lv0为同一设备

[root@localhost ~]# ls -l /dev/vg0/lv0
lrwxrwxrwx. 1 root root 7 Apr 22 07:23 /dev/vg0/lv0 -> ../dm-0
[root@localhost ~]# ls -l /dev/mapper/vg0-lv0
lrwxrwxrwx. 1 root root 7 Apr 22 07:23 /dev/mapper/vg0-lv0 -> ../dm-0

5.逻辑卷的扩展
当lv为xfs文件系统只支持增加不支持缩减；当文件系统类型为ext2、ext3、ext4 时候，既可以增加可以以减少
未扩展之前lv0分区未100M，文件系统大小为97M
（1）将lv0分区扩展至300M
lvextend -L 300M /dev/vg0/lv0 #扩大lv分区到300M

（2）改变文件系统大小与分区匹配
xfs_growfs /dev/vg0/lv0 ##扩大lv分区文件系统大小与分区大小一致

6.ext格式下逻辑卷的扩大与缩减
将设备格式化成xfs后是不能缩减的，只能扩展，所以需重新格式化逻辑卷的类型
（1）重新格式化

[root@localhost ~]# umount /mnt  ##卸载
[root@localhost ~]# df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/vda1       10473900 3176680   7297220  31% /
devtmpfs          927060       0    927060   0% /dev
tmpfs             942648     140    942508   1% /dev/shm
tmpfs             942648   17072    925576   2% /run
tmpfs             942648       0    942648   0% /sys/fs/cgroup
/dev/sr0         3704296 3704296         0 100% /run/media/root/RHEL-7.3 Server.x86_64
[root@localhost ~]# mkfs.ext4 /dev/vg0/lv0  ##格式为ext格式
mke2fs 1.42.9 (28-Dec-2013)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
76912 inodes, 307200 blocks
15360 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=33947648
38 block groups
8192 blocks per group, 8192 fragments per group
2024 inodes per group
Superblock backups stored on blocks: 
	8193, 24577, 40961, 57345, 73729, 204801, 221185

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  ##重新挂载
[root@localhost ~]# df
Filesystem          1K-blocks    Used Available Use% Mounted on
/dev/vda1            10473900 3176680   7297220  31% /
devtmpfs               927060       0    927060   0% /dev
tmpfs                  942648     140    942508   1% /dev/shm
tmpfs                  942648   17072    925576   2% /run
tmpfs                  942648       0    942648   0% /sys/fs/cgroup
/dev/sr0              3704296 3704296         0 100% /run/media/root/RHEL-7.3 Server.x86_64
/dev/mapper/vg0-lv0    289285    2062    267767   1% /mnt

（2）ext格式下逻辑卷的扩增
a.lvextend -L 400M /dev/vg0/lv0 #增加lv分区的大小到400M

b.resize2fs /dev/vg0/lv0 #扩大lv分区文件系统大小与分区大小一致

（3）ext格式下逻辑卷的缩减
文件系统的缩减不支持在挂载状态下进行，所以需要进行lv设备的缩减时需要先进行卸载设备，进行分区缩减后在进行挂载。
a.卸载

[root@localhost ~]# umount /mnt
[root@localhost ~]# df
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/vda1       10473900 3176692   7297208  31% /
devtmpfs          927060       0    927060   0% /dev
tmpfs             942648     140    942508   1% /dev/shm
tmpfs             942648   17072    925576   2% /run
tmpfs             942648       0    942648   0% /sys/fs/cgroup
/dev/sr0         3704296 3704296         0 100% /run/media/root/RHEL-7.3 Server.x86_64

b.缩减lv分区为100M
e2fsck -f /dev/vg0/lv0 #检测文件系统，确定文件系统中已有数据大小防止过度缩减

[root@localhost ~]# e2fsck -f /dev/vg0/lv0
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: 11/101200 files (0.0% non-contiguous), 23297/409600 blocks

c.resize2fs /dev/vg0/lv0 100M #缩减文件系统的大小为100M

注意：在缩减时，先缩减文件系统大小，再缩减分区；即先软件再硬件，否则会出现缩减文件大小不成功和挂载出现问题

[root@localhost ~]# mount /dev/vg0/lv0 /mnt
mount: wrong fs type, bad option, bad superblock on /dev/mapper/vg0-lv0,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try  ##挂载失败
       dmesg | tail or so.

d.重新挂载

 [root@localhost ~]# mount /dev/vg0/lv0 /mnt
[root@localhost ~]# df
Filesystem          1K-blocks    Used Available Use% Mounted on
/dev/vda1            10473900 3176844   7297056  31% /
devtmpfs               927060       0    927060   0% /dev
tmpfs                  942648     140    942508   1% /dev/shm
tmpfs                  942648   17044    925604   2% /run
tmpfs                  942648       0    942648   0% /sys/fs/cgroup
/dev/sr0              3704296 3704296         0 100% /run/media/root/RHEL-7.3 Server.x86_64
/dev/mapper/vg0-lv0     90880    1550     82460   2% /mnt

7.逻辑卷组vg大小的增加与减少
vg是由多个pv设备组成的，对vg设备大小的增加与减少其实就是对组成vg的pv设备的增加或者减少
（1）新建磁盘并改变标签为8e

[root@localhost ~]# fdisk /dev/vdb
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): 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 (1230848-20971519, default 1230848): 
Using default value 1230848
Last sector, +sectors or +size{K,M,G} (1230848-20971519, default 20971519): +1G
Partition 3 of type Linux and of size 1 GiB is set

Command (m for help): p

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: 0x29d83a76

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048      206847      102400   83  Linux
/dev/vdb2          206848     1230847      512000   8e  Linux LVM
/dev/vdb3         1230848     3327999     1048576   83  Linux

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

Command (m for help): p

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: 0x29d83a76

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048      206847      102400   83  Linux
/dev/vdb2          206848     1230847      512000   8e  Linux LVM
/dev/vdb3         1230848     3327999     1048576   8e  Linux LVM
[root@localhost ~]# partprobe
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
Warning: Unable to open /dev/sr0 read-write (Read-only file system).  /dev/sr0 has been opened read-only.
[root@localhost ~]# fdisk -l /dev/vdb

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: 0x29d83a76

   Device Boot      Start         End      Blocks   Id  System
/dev/vdb1            2048      206847      102400   83  Linux
/dev/vdb2          206848     1230847      512000   8e  Linux LVM
/dev/vdb3         1230848     3327999     1048576   8e  Linux LVM

（2）对新建分区进行物理卷 物理卷组 逻辑卷组的划分
pvcreate /dev/vdb3 ##对磁盘新的物理分区id进行修改，将其做成物理卷pv
vgextend vg0 /dev/vdb3 ##将新做成的pv添加到需要增加大小的逻辑卷组中来

（3）vg（逻辑卷组）大小的增加与减少
移除前

移除后
pvmove /dev/vdb2 /dev/vdb3 #根据各个pv空间的使用情况，将被占用的空间都集中到一个设备中，空出一个空设备

vgreduce vg0 /dev/vdb2 ##将该pv设从该vg中移出

pvremove /dev/vdb2 #再将该空pv设备恢复成物理磁盘分区

8.Lv逻辑卷快照
作用：当我们存储信息在lv分区中以后，不想分区中的文件被损坏，可以通过快照的方式创建一个副本，通过该副本可以看到源分区中的内容，但是该副本中只记录对源分区的修改，不会带源分区中的文件造成任何影响
格式：
lvcreate -L 50M -n lv0-backup -s /dev/vg0/lv0
给/dev/vg0/lv0建立快照，-L 指定快照大小，-n指定快照名字 -s指定快照模板设备

[root@localhost ~]# lvcreate -L 50M -n lv0-kz -s /dev/vg0/lv0  ##创建快照
  Rounding up size to full physical extent 52.00 MiB
  Logical volume "lv0-kz" created
[root@localhost ~]# ls /dev/mapper
control  vg0-lv0  vg0-lv0--kz  vg0-lv0--kz-cow  vg0-lv0-real  ##vg0-lv0-kz出现则创建成功
[root@localhost ~]# df  ##查看挂载
Filesystem          1K-blocks    Used Available Use% Mounted on
/dev/vda1            10473900 3177152   7296748  31% /
devtmpfs               927060       0    927060   0% /dev
tmpfs                  942648     140    942508   1% /dev/shm
tmpfs                  942648   17064    925584   2% /run
tmpfs                  942648       0    942648   0% /sys/fs/cgroup
/dev/sr0              3704296 3704296         0 100% /run/media/root/RHEL-7.3 Server.x86_64
/dev/mapper/vg0-lv0     90880    1550     82460   2% /mnt
[root@localhost ~]# touch /mnt/file{1..3}
[root@localhost ~]# ls /mnt  ##通过快照的挂载可以看到原设备中的文件
file1  file2  file3  lost+found

将快照设备挂载之后，可以看到源设备中的文件，然后在快照设备中将文件删除，卸载设备之后，删除该lv分区的快照，重新生成一个，重新挂载，仍能看到源设备中的文件，说明对源设备文件没有影响

[root@localhost ~]# cd /mnt
[root@localhost mnt]# ls
file1  file2  file3  lost+found
[root@localhost mnt]# rm -fr /mnt/*  ##在快照中删除文件
[root@localhost mnt]# ls
[root@localhost mnt]# cd
[root@localhost ~]# umount /mnt  ##卸载
[root@localhost ~]# lvremove /dev/vg0/lv0-kz  ##删除快照
Do you really want to remove active logical volume lv0-kz? [y/n]: y
  Logical volume "lv0-kz" successfully removed
[root@localhost ~]# lvcreate -L 50M -n lv0-kz -s /dev/vg0/lv0  ##重新创建快照
  Rounding up size to full physical extent 52.00 MiB
  Logical volume "lv0-kz" created
[root@localhost ~]# mount /dev/vg0/lv0-kz /mnt  ##重新挂载
[root@localhost ~]# cd /mnt
[root@localhost mnt]# ls  ##仍旧可以看到设备中的文件
file1  file2  file3  lost+found

6.LVM的删除
删除顺序：lvremove ##删除逻辑卷–vgremove ##删除逻辑卷组–pvremove ##删除物理卷

[root@localhost ~]# umount /mnt
[root@localhost ~]# lvremove /dev/vg0/lv0-kz  ##删除快照
Do you really want to remove active logical volume lv0-backup? [y/n]: y
  Logical volume "lv0-kz" 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  ##删除逻辑卷组
  Volume group "vg0" successfully removed
 [root@localhost ~]# pvremove /dev/vdb3  ##删除物理卷
  Labels on physical volume "/dev/vdb3" successfully wiped
[root@localhost ~]# lvs  ##查看逻辑卷组
  No volume groups found
[root@localhost ~]# vgs  ##查看逻辑卷
  No volume groups found
[root@localhost ~]# pvs  ##查看物理卷