1. 理解LVM工作原理
什么是LVM？
LVM是逻辑盘卷管理（Logical Volume Manager）的简称，它是Linux环境下对磁盘分区进行管理的一种机制，LVM是建立在硬盘和分区之上的一个逻辑层，来提高磁盘分区管理的灵活性。
为什么要使用LVM？
在日常工作或者学习中，随着电脑的不断被使用，我们的磁盘空间可能会越来越小，这时候，我们不能直接更换大硬盘，因为硬盘有价，数据无价，这时候我们就可以使用LVM，LVM将存储虚拟化,使用逻辑卷,你不会受限于物理磁盘的大小,另外,和硬件相关的存储设置被其隐藏,你能不用停止应用或卸载文件系统来调整卷大小或数据迁移.这样能减少操作成本，LVM最大的特点就是可以对磁盘进行动态管理。因为逻辑卷的大小是可以动态调整的，而且不会丢失现有的数据。如果我们新增加了硬盘，其也不会改变现有上层的逻辑卷。作为一个动态磁盘管理机制，逻辑卷技术大大提高了磁盘管理的灵活性。
LVM工作机制？
LVM就是通过将底层的物理硬盘抽象的封装起来，然后以逻辑卷的方式呈现给上层应用。在传统的磁盘管理机制中，我们的上层应用是直接访问文件系统，从而对底层的物理硬盘进行读取，而在LVM中，其通过对底层的硬盘进行封装，当我们对底层的物理硬盘进行操作时，其不再是针对于分区进行操作，而是通过一个叫做逻辑卷的东西来对其进行底层的磁盘管理操作。
逻辑卷管理概念？
物理卷（PV, Physical Volume）
物理卷就是指磁盘,磁盘分区或从逻辑上和磁盘分区具有同样功能的设备(如RAID)，是LVM的基本存储逻辑块，但和基本的物理存储介质（如分区、磁盘等）比较，却包含有和LVM相关的管理参数。当前LVM允许你在每个物理卷上保存这个物理卷的0至2份元数据拷贝.默认为1,保存在设备的开始处.为2时,在设备结束处保存第二份备份.
卷组（VG, Volume Group）
LVM卷组类似于非LVM系统中的物理硬盘，其由物理卷组成。能在卷组上创建一个或多个“LVM分区”（逻辑卷），LVM卷组由一个或多个物理卷组成。
逻辑卷（LV, Logical Volume）
LVM的逻辑卷类似于非LVM系统中的硬盘分区，在逻辑卷之上能建立文件系统(比如/home或/usr等)。
LVM原理图
2. LVM操作案例分析
添加磁盘并创建一个分区
[root@localhost ~]# fdisk -l //查看磁盘情况
[root@localhost ~]# fdisk /dev/sdb //进入磁盘（可以依次按键n-->e-->回车-->回车-->w,即用此磁盘空闲空间创建分区）
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.
Device does not contain a recognized partition table
Building a new DOS disklabel with disk identifier 0xeed8cf69.
Command (m for help): p //查看分区列表
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: 0xeed8cf69
Device Boot Start End Blocks Id System
Command (m for help): n //添加一个分区
Partition type:
p primary (0 primary, 0 extended, 4 free)
e extended
Select (default p):
Using default response p
Partition number (1-4, default 1): +20G
Partition number (1-4, default 1):
First sector (2048-104857599, default 2048):
Using default value 2048
Last sector, +sectors or +size{K,M,G} (2048-104857599, default 104857599): +20G
Partition 1 of type Linux and of size 20 GiB is set
Command (m for help): t //更改分区类型
Selected partition 1
Hex code (type L to list all codes): l //分区类型列表
Hex code (type L to list all codes): 8e //将新添加的分区标注成LVM,只要是‘8e’(LVM)类型的磁盘分区都可以用来扩展卷组。
Changed type of partition 'Linux' to 'Linux LVM'
Command (m for help): p //查看分区表
Disk /dev/sdb: 53.7 GB, 53687091200 bytes, 104857600 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: 0xeed8cf69
Device Boot Start End Blocks Id System
/dev/sdb1 2048 41945087 20971520 8e Linux LVM
Command (m for help): w //保存
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
创建逻辑卷lv01并挂载到/lvm01目录上。
[root@localhost ~]# pvcreate /dev/sdb1 //创建物理卷
Physical volume "/dev/sdb1" successfully created
[root@localhost ~]# mkfs.ext4 /dev/sdb1 //格式化新添加的分区
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
1310720 inodes, 5242880 blocks
262144 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2153775104
160 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, 1605632, 2654208,
4096000
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# pvcreate /dev/sdb1 //创建pv
WARNING: ext4 signature detected on /dev/sdb1 at offset 1080. Wipe it? [y/n]: y
Wiping ext4 signature on /dev/sdb1.
Physical volume "/dev/sdb1" successfully created
[root@localhost ~]# pvdisplay /dev/sdb1 //查看pv信息
"/dev/sdb1" is a new physical volume of "20.00 GiB"
--- NEW Physical volume ---
PV Name /dev/sdb1
VG Name
PV Size 20.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID cL1S1N-nUGj-DuYa-9RP0-ened-A4ZZ-FTlOWX
[root@localhost ~]# vgcreate vg01 /dev/sdb1
Volume group "vg01" successfully created
[root@localhost ~]# vgdisplay vg01
--- Volume group ---
VG Name vg01
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 1
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 0
Open LV 0
Max PV 0
Cur PV 1
Act PV 1
VG Size 20.00 GiB
PE Size 4.00 MiB
Total PE 5119
Alloc PE / Size 0 / 0
Free PE / Size 5119 / 20.00 GiB
VG UUID lghbtI-4usq-GFEj-Zr26-7NrP-UUE3-0RHMF5
[root@localhost ~]# lvcreate -L 10M -n lv01 vg01 //从卷组vg01中创建一个大小为10M名字为lv01的逻辑卷， 如果要使用卷组剩下的所有空间创建逻辑卷 lvcreate -n lv-name -l 100%FREE vg-name
Rounding up size to full physical extent 12.00 MiB
Logical volume "lv01" created.
[root@localhost ~]# lvdisplay vg01 //查看在vg01组创建的逻辑卷
--- Logical volume ---
LV Path /dev/vg01/lv01
LV Name lv01
VG Name vg01
LV UUID A1CBRX-wLOF-2d7D-SPvg-sBhD-3wzO-WtbmeH
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2020-01-14 17:08:48 +0800
LV Status available
# open 0
LV Size 12.00 MiB
Current LE 3
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:3
[root@localhost ~]# mkfs.ext4 /dev/vg01/lv01 //逻辑卷已经准备好了，我们可以格式化和挂载逻辑卷，就像其它ext2/3/4分区一样！
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
3072 inodes, 12288 blocks
614 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=12582912
2 block groups
8192 blocks per group, 8192 fragments per group
1536 inodes per group
Superblock backups stored on blocks:
8193
Allocating group tables: done
Writing inode tables: done
Creating journal (1024 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# mkdir /lvm01
[root@localhost ~]# mount /dev/vg01/lv01 /lvm01/
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 50G 845M 50G 2% /
devtmpfs 3.9G 0 3.9G 0% /dev
tmpfs 3.9G 0 3.9G 0% /dev/shm
tmpfs 3.9G 8.6M 3.9G 1% /run
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/mapper/centos-home 42G 33M 42G 1% /home
/dev/sda1 497M 123M 375M 25% /boot
tmpfs 781M 0 781M 0% /run/user/0
/dev/mapper/vg01-lv01 11M 204K 9.6M 3% /lvm01
扩展LVM空间
逻辑卷lv01只有16MB的空间，我们需要对其进行扩展空间，扩展空间并不会影响到之前存储的数据。
实际情景1：卷组vg01有空闲的空间，直接进行扩展就可以。
[root@localhost ~]# lvextend -L +200M /dev/vg01/lv01 //使用lvextend命令直接对逻辑卷进行扩展200M Size of logical volume vg01/lv01 changed from 52.00 MiB (13 extents) to 252.00 MiB (63 extents). Logical volume lv01 successfully resized. [root@localhost ~]# df -Th //发现分区大小并没有改变 Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/centos-root xfs 50G 845M 50G 2% / devtmpfs devtmpfs 3.9G 0 3.9G 0% /dev tmpfs tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs tmpfs 3.9G 8.6M 3.9G 1% /run tmpfs tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup /dev/mapper/centos-home xfs 42G 33M 42G 1% /home /dev/sda1 xfs 497M 123M 375M 25% /boot tmpfs tmpfs 781M 0 781M 0% /run/user/0 /dev/mapper/vg01-lv01 ext4 50M 396K 46M 1% /lvm01 [root@localhost ~]# resize2fs /dev/vg01/lv01 //激活 resize2fs 1.42.9 (28-Dec-2013) Filesystem at /dev/vg01/lv01 is mounted on /lvm01; on-line resizing required old_desc_blocks = 1, new_desc_blocks = 2 The filesystem on /dev/vg01/lv01 is now 258048 blocks long. [root@localhost ~]# df -Th //可以看到/lvm01正常了 Filesystem Type Size Used Avail Use% Mounted on /dev/mapper/centos-root xfs 50G 845M 50G 2% / devtmpfs devtmpfs 3.9G 0 3.9G 0% /dev tmpfs tmpfs 3.9G 0 3.9G 0% /dev/shm tmpfs tmpfs 3.9G 8.6M 3.9G 1% /run tmpfs tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup /dev/mapper/centos-home xfs 42G 33M 42G 1% /home /dev/sda1 xfs 497M 123M 375M 25% /boot tmpfs tmpfs 781M 0 781M 0% /run/user/0 /dev/mapper/vg01-lv01 ext4 245M 768K 233M 1% /lvm01
实际情景2：卷组vg01空间不足，先扩展vg，扩展vg就是往vg中加pv
使用fdisk命令创建一个分区
[root@localhost ~]# fdisk /dev/sdc Command (m for help): n Partition type: p primary (0 primary, 0 extended, 4 free) e extended Select (default p): 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. [root@localhost ~]# fdisk /dev/sdc 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): p Disk /dev/sdc: 85.9 GB, 85899345920 bytes, 167772160 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: 0xeeb944e3 Device Boot Start End Blocks Id System /dev/sdc1 2048 167772159 83885056 8e Linux LVM
添加物理卷并添加到卷组vg01中，然后再进行逻辑卷扩容操作
[root@localhost ~]# pvcreate /dev/sdc1 //创建物理卷
Physical volume "/dev/sdc1" successfully created
[root@localhost ~]# mkfs.ext4 /dev/sdc1
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
5242880 inodes, 20971264 blocks
1048563 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2168455168
640 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, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# mkfs.ext4 /dev/sdc1
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
5242880 inodes, 20971264 blocks
1048563 blocks (5.00%) reserved for the super user
First data block=0
Maximum filesystem blocks=2168455168
640 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, 1605632, 2654208,
4096000, 7962624, 11239424, 20480000
Allocating group tables: done
Writing inode tables: done
Creating journal (32768 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# vgextend vg01 /dev/sdc1 //将物理卷/dev/sdc1添加到vg01卷组里面
WARNING: ext4 signature detected on /dev/sdc1 at offset 1080. Wipe it? [y/n]: y
Wiping ext4 signature on /dev/sdc1.
Physical volume "/dev/sdc1" successfully created
Volume group "vg01" successfully extended
[root@localhost ~]# lvextend -L +15G /dev/vg01/lv02 //扩容
Size of logical volume vg01/lv02 changed from 19.75 GiB (5056 extents) to 34.75 GiB (8896 extents).
Logical volume lv02 successfully resized.
[root@localhost ~]# resize2fs /dev/vg01/lv02
resize2fs 1.42.9 (28-Dec-2013)
Filesystem at /dev/vg01/lv02 is mounted on /lvm02; on-line resizing required
old_desc_blocks = 3, new_desc_blocks = 5
The filesystem on /dev/vg01/lv02 is now 9109504 blocks long.
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 50G 845M 50G 2% /
devtmpfs 3.9G 0 3.9G 0% /dev
tmpfs 3.9G 0 3.9G 0% /dev/shm
tmpfs 3.9G 8.6M 3.9G 1% /run
tmpfs 3.9G 0 3.9G 0% /sys/fs/cgroup
/dev/mapper/centos-home 42G 33M 42G 1% /home
/dev/sda1 497M 123M 375M 25% /boot
tmpfs 781M 0 781M 0% /run/user/0
/dev/mapper/vg01-lv01 245M 768K 233M 1% /lvm01
/dev/mapper/vg01-lv02 35G 48M 33G 1% /lvm02