一、简单的原理图

LVM（Logical volume Manager）逻辑卷管理通过将底层物理硬盘抽象封装起来，以逻辑卷的形式表现给上层系统，逻辑卷的大小可以动态调整，而且不会丢失现有数据。新加入的硬盘也不会改变现有上层的逻辑卷。

作为一种动态磁盘管理机制，逻辑卷技术大大提高了磁盘管理的灵活性。

PE  （ physical extend） 物理扩展，是逻辑卷磁盘管理的基础单位，默认是4M大小
PV  （physical volumes） 物理卷
VG （volume groups）     卷组
LV  （logical volumes）  逻辑卷

二、创建LVM

在虚拟机中增加两块10G的磁盘/dev/sdb和/dev/sdc

[root@localhost ~]# yum install lvm2 -y                # 如果是最小化安装系统，需要先安装lvm2

[root@localhost ~]# pvcreate /dev/sdb /dev/sdc         # 将一块或多块物理磁盘初始化为物理卷
  Physical volume "/dev/sdb" successfully created.
  Physical volume "/dev/sdc" successfully created.

[root@localhost ~]# vgcreate lzfn /dev/sdb /dev/sdc    # 创建卷组，并将PV加入到卷组中
  Volume group "lzfn" successfully created

[root@localhost ~]# lvcreate -n data01 -L 2G lzfn      # 基于卷组创建逻辑卷data01，大小设置为2G
  Logical volume "data01" created.

[root@localhost ~]# mkfs.ext4 /dev/lzfn/data01         # 将创建好的逻辑卷格式化文件系统 
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
131072 inodes, 524288 blocks
26214 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=536870912
16 block groups
32768 blocks per group, 32768 fragments per group
8192 inodes per group
Superblock backups stored on blocks: 
    32768, 98304, 163840, 229376, 294912

Allocating group tables: done                            
Writing inode tables: done                            
Creating journal (16384 blocks): done
Writing superblocks and filesystem accounting information: done 

[root@localhost ~]# mkdir /data01
[root@localhost ~]# mount /dev/lzfn/data01 /data01/      #　挂载到目录进行使用
[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/sda3                 28G  1.2G   27G   5% /
devtmpfs                 479M     0  479M   0% /dev
tmpfs                    489M     0  489M   0% /dev/shm
tmpfs                    489M  6.7M  482M   2% /run
tmpfs                    489M     0  489M   0% /sys/fs/cgroup
/dev/sda1                 97M   92M  4.9M  95% /boot
tmpfs                     98M     0   98M   0% /run/user/0
/dev/mapper/lzfn-data01  2.0G  6.0M  1.8G   1% /data01

三、查看LVM

# 查看物理卷信息
[root@localhost ~]# pvdisplay     # 详细
  --- Physical volume ---
  PV Name               /dev/sdb
  VG Name               lzfn
  PV Size               10.00 GiB / not usable 4.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              2559
  Free PE               2047
  Allocated PE          512
  PV UUID               YtXz3s-LbJK-4WcI-FcHh-WYh3-CfGU-B2l2yw
   
  --- Physical volume ---
  PV Name               /dev/sdc
  VG Name               lzfn
  PV Size               10.00 GiB / not usable 4.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              2559
  Free PE               2559
  Allocated PE          0
  PV UUID               eyLvyn-ckUh-8ES1-ejdh-JZaU-vc8x-NYwoeV
   
[root@localhost ~]# pvs            # 简单
  PV         VG   Fmt  Attr PSize   PFree  
  /dev/sdb   lzfn lvm2 a--  <10.00g  <8.00g
  /dev/sdc   lzfn lvm2 a--  <10.00g <10.00g

# 查看卷组信息
[root@localhost ~]# vgdisplay 
  --- Volume group ---
  VG Name               lzfn
  System ID             
  Format                lvm2
  Metadata Areas        2
  Metadata Sequence No  2
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                1
  Open LV               1
  Max PV                0
  Cur PV                2
  Act PV                2
  VG Size               19.99 GiB
  PE Size               4.00 MiB
  Total PE              5118
  Alloc PE / Size       512 / 2.00 GiB
  Free  PE / Size       4606 / 17.99 GiB
  VG UUID               qQjlvL-k10O-N23m-J9zV-6ufY-Xzzx-QYzLJX
   
[root@localhost ~]# vgs
  VG   #PV #LV #SN Attr   VSize  VFree 
  lzfn   2   1   0 wz--n- 19.99g 17.99g

# 查看逻辑卷信息
[root@localhost ~]# lvdisplay 
  --- Logical volume ---
  LV Path                /dev/lzfn/data01
  LV Name                data01
  VG Name                lzfn
  LV UUID                mmpUBB-4uMY-HLlL-8EBm-1CIP-GYi1-Mvjvdx
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2021-09-28 22:32:25 +0800
  LV Status              available
  # open                 1
  LV Size                2.00 GiB
  Current LE             512
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:0
   
[root@localhost ~]# lvs
  LV     VG   Attr       LSize Pool Origin Data%  Meta%  Move Log Cpy%Sync Convert
  data01 lzfn -wi-ao---- 2.00g    

四、删除LVM

一定要按此顺序删除，如果要删除卷组，就要先把逻辑卷删除完成之后，才能继续删除卷组，最后是物理卷。

[root@localhost ~]# umount /data01 
[root@localhost ~]# lvremove /dev/lzfn/data01 
Do you really want to remove active logical volume lzfn/data01? [y/n]: y
  Logical volume "data01" successfully removed
[root@localhost ~]# vgremove lzfn 
  Volume group "lzfn" successfully removed
[root@localhost ~]# pvremove /dev/sdb /dev/sdc
  Labels on physical volume "/dev/sdb" successfully wiped.
  Labels on physical volume "/dev/sdc" successfully wiped.

五、扩展逻辑卷

 将data01由5G扩容到9G

[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/sda3                 28G  1.2G   27G   5% /
devtmpfs                 479M     0  479M   0% /dev
tmpfs                    489M     0  489M   0% /dev/shm
tmpfs                    489M  6.8M  482M   2% /run
tmpfs                    489M     0  489M   0% /sys/fs/cgroup
/dev/sda1                 97M   92M  4.9M  95% /boot
tmpfs                     98M     0   98M   0% /run/user/0
/dev/mapper/lzfn-data01  4.8G   20M  4.6G   1% /data01        # 要扩容的逻辑卷 

[root@localhost ~]# vgs          # 查看是否还有可用卷组空间进行扩容
  VG   #PV #LV #SN Attr   VSize  VFree 
  lzfn   2   1   0 wz--n- 19.99g 14.99g

[root@localhost ~]# lvextend -L +4G /dev/lzfn/data01           # 将逻辑卷扩容4G，也可以使用 -n lzfn 参数
  Size of logical volume lzfn/data01 changed from 5.00 GiB (1280 extents) to 9.00 GiB (2304 extents).
  Logical volume lzfn/data01 successfully resized.

[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/sda3                 28G  1.2G   27G   5% /
devtmpfs                 479M     0  479M   0% /dev
tmpfs                    489M     0  489M   0% /dev/shm
tmpfs                    489M  6.7M  482M   2% /run
tmpfs                    489M     0  489M   0% /sys/fs/cgroup
/dev/sda1                 97M   92M  4.9M  95% /boot
tmpfs                     98M     0   98M   0% /run/user/0
/dev/mapper/lzfn-data01  4.8G   20M  4.6G   1% /data01

[root@localhost ~]# resize2fs /dev/lzfn/data01                   # 扩容后要调整文件系统后才会生效
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/lzfn/data01 is mounted on /data01; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/lzfn/data01 is now 2359296 blocks long.

[root@localhost ~]# df -h
Filesystem               Size  Used Avail Use% Mounted on
/dev/sda3                 28G  1.2G   27G   5% /
devtmpfs                 479M     0  479M   0% /dev
tmpfs                    489M     0  489M   0% /dev/shm
tmpfs                    489M  6.7M  482M   2% /run
tmpfs                    489M     0  489M   0% /sys/fs/cgroup
/dev/sda1                 97M   92M  4.9M  95% /boot
tmpfs                     98M     0   98M   0% /run/user/0
/dev/mapper/lzfn-data01  8.8G   23M  8.3G   1% /data01

六、扩展一个PV

再将一块10G的磁盘加入到物理卷中

[root@localhost ~]# fdisk -l /dev/sdd

Disk /dev/sdd: 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

[root@localhost ~]# pvs
  PV         VG   Fmt  Attr PSize   PFree   
  /dev/sdb   lzfn lvm2 a--  <10.00g 1020.00m
  /dev/sdc   lzfn lvm2 a--  <10.00g  <10.00g
[root@localhost ~]# pvcreate /dev/sdd            # 将要添加的vg硬盘格式化成pv
  Physical volume "/dev/sdd" successfully created.

[root@localhost ~]# vgextend lzfn /dev/sdd       # 将新的pv加到指定卷组中
  Volume group "lzfn" successfully extended

[root@localhost ~]# vgs                          # 扩容成功
  VG   #PV #LV #SN Attr   VSize   VFree  
  lzfn   3   1   0 wz--n- <29.99g <20.99g

[root@localhost ~]# pvs                          # 已经扩容成功
  PV         VG   Fmt  Attr PSize   PFree   
  /dev/sdb   lzfn lvm2 a--  <10.00g 1020.00m
  /dev/sdc   lzfn lvm2 a--  <10.00g  <10.00g
  /dev/sdd   lzfn lvm2 a--  <10.00g  <10.00g