LVM（逻辑卷管理器）
逻辑卷管理器是Linux系统用于对硬盘分区进行管理的一种机制，理论性较强，其创建初衷是为了解决硬盘设备在创建分区后不易修改分区大小的缺陷。尽管对传统的硬盘分区进行强制扩容或缩容从理论上来讲是可行的，但是却可能造成数据的丢失。而LVM技术是在硬盘分区和文件系统之间添加了一个逻辑层，它提供了一个抽象的卷组，可以把多块硬盘进行卷组合并。这样一来，用户不必关心物理硬盘设备的底层架构和布局，就可以实现对硬盘分区的动态调整。
物理卷处于LVM中的最底层，可以将其理解为物理硬盘、硬盘分区或者RAID磁盘阵列，这都可以。卷组建立在物理卷之上，一个卷组可以包含多个物理卷，而且在卷组创建之后也可以继续向其中添加新的物理卷。逻辑卷是用卷组中空闲的资源建立的，并且逻辑卷在建立后可以动态地扩展或缩小空间。这就是LVM的核心理念。
PE最小存储单元，VG通过PV组合好PE，成一个整的；然后LV从VG分出来可供挂载使用
部署逻辑卷
常用的LVM部署命令
| 功能/命令 | 物理卷管理 | 卷组管理 | 逻辑卷管理 |
|---|---|---|---|
| 扫描 | pvscan | vgscan | lvscan |
| 建立 | pvcreate | vgcreate | lvcreate |
| 显示 | pvdisplay | vgdisplay | lvdisplay |
| 删除 | pvremove | vgremove | lvremove |
| 扩展 | vgextend | lvextend | |
| 缩小 | vgreduce | lvreduce |
为了避免多个实验之间相互发生冲突，请大家自行将虚拟机还原到初始状态，并在虚拟机中添加两块新硬盘设备，然后开机
第1步：让新添加的两块硬盘设备支持LVM技术
[root@localhost ~]# pvcreate /dev/sdb /dev/sdc
Physical volume "/dev/sdb" successfully created.
Physical volume "/dev/sdc" successfully created.
#有时候创建不成功，有残留数据需要重新做分区表
#[root@localhost ~]#parted /dev/sd[b-c] mklabel msdos
第2步：把两块硬盘设备加入到storage卷组中，然后查看卷组的状态
[root@localhost ~]# vgcreate storage /dev/sdb /dev/sdc
Volume group "storage" successfully created
[root@localhost ~]# vgdisplay storage
--- Volume group ---
VG Name centos
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 3
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 1
Act PV 1
VG Size <19.00 GiB
PE Size 4.00 MiB
Total PE 4863
Alloc PE / Size 4863 / <19.00 GiB
Free PE / Size 0 / 0
VG UUID hXvPk7-ey0X-GUp1-NesK-9ty4-LVMc-6FUtwh
--- Volume group ---
VG Name storage
System ID
Format lvm2
Metadata Areas 2
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 2
Act PV 2
VG Size 39.99 GiB
PE Size 4.00 MiB
Total PE 10238
Alloc PE / Size 0 / 0
Free PE / Size 10238 / 39.99 GiB
VG UUID R3Lgwt-YdRK-3Qhx-vzzt-P4gM-yxbZ-VbeojU
第3步：切割出一个约为150MB的逻辑卷设备。
这里需要注意切割单位的问题。在对逻辑卷进行切割时有两种计量单位。
第一种是以容量为单位，所使用的参数为-L。例如，使用-L 150M生成一个大小为150MB的逻辑卷。
另外一种是以基本单元的个数为单位，所使用的参数为-l。每个基本单元的大小默认为4MB。例如，使用-l 37可以生成一个大小为37×4MB=148MB的逻辑卷。
# [root@localhost ~]# lvcreate -n vo -l 37 -I 8M storage
[root@localhost ~]# lvcreate -n vo -l 37 storage
Logical volume "vo" created.
# 每个PE占4M，37*4=148M，远少于sdb的20G，不会占用到第二个PV（sdc），所以lsblk只看到占用了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
└─storage-vo 253:2 0 148M 0 lvm
sdc 8:32 0 20G 0 disk
sdd 8:48 0 20G 0 disk
sde 8:64 0 20G 0 disk
sr0 11:0 1 1024M 0 rom
[root@localhost ~]# lvdisplay
--- Logical volume ---
LV Path /dev/centos/swap
LV Name swap
VG Name centos
LV UUID RHOW0p-W5MW-lfGs-rIFk-tcmK-bKsd-bdh3ej
LV Write Access read/write
LV Creation host, time localhost, 2019-04-15 17:30:59 +0800
LV Status available
# open 2
LV Size 2.00 GiB
Current LE 512
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:1
--- Logical volume ---
LV Path /dev/centos/root
LV Name root
VG Name centos
LV UUID u4rM0M-cE5q-ii2n-j7Bd-eXvd-Gsw0-8ByOgp
LV Write Access read/write
LV Creation host, time localhost, 2019-04-15 17:31:00 +0800
LV Status available
# open 1
LV Size <17.00 GiB
Current LE 4351
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
--- Logical volume ---
LV Path /dev/storage/vo
LV Name vo
VG Name storage
LV UUID WP06I4-XA8u-mGqT-uFEZ-uhyN-nbrT-ehKMTe
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2019-04-18 13:37:34 +0800
LV Status available
# open 0
LV Size 148.00 MiB
Current LE 37
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:2
第4步：把生成好的逻辑卷进行格式化，然后挂载使用。
[root@localhost ~]# mkfs.ext4 /dev/storage/vo
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
38000 inodes, 151552 blocks
7577 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=33816576
19 block groups
8192 blocks per group, 8192 fragments per group
2000 inodes per group
Superblock backups stored on blocks:
8193, 24577, 40961, 57345, 73729
Allocating group tables: done
Writing inode tables: done
Creating journal (4096 blocks): done
Writing superblocks and filesystem accounting information: done
[root@localhost ~]# mkdir /mnt/vo
[root@localhost ~]# mount /dev/storage/vo /mnt/vo
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 17G 1003M 17G 6% /
devtmpfs 898M 0 898M 0% /dev
tmpfs 910M 0 910M 0% /dev/shm
tmpfs 910M 9.5M 901M 2% /run
tmpfs 910M 0 910M 0% /sys/fs/cgroup
/dev/sda1 1014M 146M 869M 15% /boot
tmpfs 182M 0 182M 0% /run/user/0
/dev/mapper/storage-vo 140M 1.6M 128M 2% /vo
[root@localhost ~]# echo "/dev/storage/vo /mnt/vo ext4 defaults 0 0" >> /etc/fstab
扩容逻辑卷
第1步：把上一个实验中的逻辑卷vo扩展至290MB
[root@localhost ~]# umount /mnt/vo
[root@localhost ~]# lvextend -L 290M /dev/storage/vo
Rounding size to boundary between physical extents: 292.00 MiB.
Size of logical volume storage/vo changed from 148.00 MiB (37 extents) to 292.00 MiB (73 extents).
Logical volume storage/vo successfully resized.
第2步：检查硬盘完整性，并重置硬盘容量，否则挂载了还是148M
[root@localhost ~]# e2fsck -f /dev/storage/vo
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/storage/vo: 11/38000 files (0.0% non-contiguous), 10453/151552 blocks
[root@localhost ~]# resize2fs /dev/storage/vo
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/storage/vo to 299008 (1k) blocks.
The filesystem on /dev/storage/vo is now 299008 blocks long.
第3步：重新挂载硬盘设备并查看挂载状态
[root@localhost ~]# mount -a
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 17G 1003M 17G 6% /
devtmpfs 898M 0 898M 0% /dev
tmpfs 910M 0 910M 0% /dev/shm
tmpfs 910M 9.5M 901M 2% /run
tmpfs 910M 0 910M 0% /sys/fs/cgroup
/dev/sda1 1014M 146M 869M 15% /boot
tmpfs 182M 0 182M 0% /run/user/0
/dev/mapper/storage-vo 279M 2.1M 259M 1% /vo
第4步，如果扩容到30G，则会占用到sdc的pv
[root@localhost ~]# umount /mnt/vo
[root@localhost ~]# lvextend -L 30G /dev/storage/vo
[root@localhost ~]# e2fsck -f /dev/storage/vo
[root@localhost ~]# resize2fs /dev/storage/vo
[root@localhost ~]# mount -a
[root@Centos7-VM-1 ~]# 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
└─storage-vo 253:2 0 30G 0 lvm /mnt/vo
sdc 8:32 0 20G 0 disk
└─storage-vo 253:2 0 30G 0 lvm /mnt/vo
sdd 8:48 0 20G 0 disk
sde 8:64 0 20G 0 disk
sr0 11:0 1 1024M 0 rom
缩小逻辑卷
第1步：检查文件系统的完整性
[root@localhost ~]# umount /mnt/vo
[root@localhost ~]# e2fsck -f /dev/storage/vo
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/storage/vo: 11/74000 files (0.0% non-contiguous), 15507/299008 blocks
第2步：把逻辑卷vo的容量减小到120MB
[root@localhost ~]# resize2fs /dev/storage/vo 120M
resize2fs 1.42.9 (28-Dec-2013)
Resizing the filesystem on /dev/storage/vo to 122880 (1k) blocks.
The filesystem on /dev/storage/vo is now 122880 blocks long.
[root@localhost ~]# lvreduce -L 120M /dev/storage/vo
WARNING: Reducing active logical volume to 120.00 MiB.
THIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce storage/vo? [y/n]: y
Size of logical volume storage/vo changed from 292.00 MiB (73 extents) to 120.00 MiB (30 extents).
Logical volume storage/vo successfully resized.
第3步：重新挂载文件系统并查看系统状态
[root@localhost ~]# mount -a
[root@localhost ~]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 17G 1003M 17G 6% /
devtmpfs 898M 0 898M 0% /dev
tmpfs 910M 0 910M 0% /dev/shm
tmpfs 910M 9.5M 901M 2% /run
tmpfs 910M 0 910M 0% /sys/fs/cgroup
/dev/sda1 1014M 146M 869M 15% /boot
tmpfs 182M 0 182M 0% /run/user/0
/dev/mapper/storage-vo 113M 1.6M 103M 2% /vo
逻辑卷快照
LVM还具备有“快照卷”功能，该功能类似于虚拟机软件的还原时间点功能。例如，可以对某一个逻辑卷设备做一次快照，如果日后发现数据被改错了，就可以利用之前做好的快照卷进行覆盖还原。LVM的快照卷功能有两个特点：
- 快照卷的容量必须等同于逻辑卷的容量；
- 快照卷仅一次有效，一旦执行还原操作后则会被立即自动删除。
[root@localhost ~]# vgdisplay
--- Volume group ---
VG Name storage
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 4
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 39.99 GiB
PE Size 4.00 MiB
Total PE 10238
Alloc PE / Size 30 / 120.00 MiB
Free PE / Size 10208 / <39.88 GiB //容量剩余39.88G
VG UUID R3Lgwt-YdRK-3Qhx-vzzt-P4gM-yxbZ-VbeojU
接下来用重定向往逻辑卷设备所挂载的目录中写入一个文件
[root@localhost ~]# echo "hello world" > /mnt/vo/readme.txt
[root@localhost ~]# ls -l /mnt/vo
total 14
drwx------. 2 root root 12288 Apr 18 13:38 lost+found
-rw-r--r--. 1 root root 12 Apr 18 13:48 readme.txt
第1步：使用-s参数生成一个快照卷，使用-L参数指定切割的大小。
另外，还需要在命令后面写上是针对哪个逻辑卷执行的快照操作。强烈建议快照大小和原来的LVM一样大
[root@localhost ~]# lvcreate -L 120M -s -n SNAP /dev/storage/vo
#强烈建议快照大小和原来的LVM一样大，虽然指定大小是120M，并不是创建一个120M大小的快照，除非修改、新增的文件超出120M才会出事情，删除不影响。
Logical volume "SNAP" created.
[root@localhost ~]# lvdisplay
--- Logical volume ---
LV Path /dev/storage/vo
LV Name vo
VG Name storage
LV UUID WP06I4-XA8u-mGqT-uFEZ-uhyN-nbrT-ehKMTe
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2019-04-18 13:37:34 +0800
LV snapshot status source of
SNAP [active]
LV Status available
# open 1
LV Size 120.00 MiB
Current LE 30
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:2
--- Logical volume ---
LV Path /dev/storage/SNAP
LV Name SNAP
VG Name storage
LV UUID WUhSh5-GVZx-VNs5-ChOd-2EKo-50Pj-N5VDFH
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2019-04-18 13:50:24 +0800
LV snapshot status active destination for vo
LV Status available
# open 0
LV Size 120.00 MiB
Current LE 30
COW-table size 120.00 MiB
COW-table LE 30
Allocated to snapshot 0.01%
Snapshot chunk size 4.00 KiB
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:5
第2步：在逻辑卷所挂载的目录中创建一个100MB的垃圾文件，然后再查看快照卷的状态。可以发现存储空间占的用量上升了
[root@localhost ~]# dd if=/dev/zero of=/mnt/vo/files count=1 bs=100M
1+0 records in
1+0 records out
104857600 bytes (105 MB) copied, 3.29409 s, 31.8 MB/s
[root@localhost ~]# lvdisplay
--- Logical volume ---
LV Path /dev/storage/vo
LV Name vo
VG Name storage
LV UUID WP06I4-XA8u-mGqT-uFEZ-uhyN-nbrT-ehKMTe
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2019-04-18 13:37:34 +0800
LV snapshot status source of
SNAP [active]
LV Status available
# open 1
LV Size 120.00 MiB
Current LE 30
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:2
--- Logical volume ---
LV Path /dev/storage/SNAP
LV Name SNAP
VG Name storage
LV UUID WUhSh5-GVZx-VNs5-ChOd-2EKo-50Pj-N5VDFH
LV Write Access read/write
LV Creation host, time localhost.localdomain, 2019-04-18 13:50:24 +0800
LV snapshot status active destination for vo
LV Status available
# open 0
LV Size 120.00 MiB
Current LE 30
COW-table size 120.00 MiB
COW-table LE 30
Allocated to snapshot 83.71%
Snapshot chunk size 4.00 KiB
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:5
第3步：为了校验SNAP快照卷的效果，需要对逻辑卷进行快照还原操作。在此之前记得先卸载掉逻辑卷设备与目录的挂载。
[root@localhost ~]# umount /mnt/vo
[root@localhost ~]# lvconvert --merge /dev/storage/SNAP
Merging of volume storage/SNAP started.
storage/vo: Merged: 31.39%
storage/vo: Merged: 100.00%
第4步：快照卷会被自动删除掉，并且刚刚在逻辑卷设备被执行快照操作后再创建出来的100MB的垃圾文件也被清除了
[root@localhost ~]# mount -a
[root@localhost ~]# ls /vo/
lost+found readme.txt
如果修改的文件超过120M，则不可能还原快照成功
[root@Centos7-VM-1 ~]# lvcreate -L 120M -s -n SNAP /dev/storage/vo
Logical volume "SNAP" created.
[root@Centos7-VM-1 ~]# dd if=/dev/zero of=/mnt/vo/files count=2 bs=128M
记录了2+0 的读入
记录了2+0 的写出
268435456字节(268 MB)已复制，2.34164 秒，115 MB/秒
[root@Centos7-VM-1 ~]# lvdisplay storage
--- Logical volume ---
LV Path /dev/storage/vo
LV Name vo
VG Name storage
LV UUID TRYAMX-buf7-8SUg-1u5r-BmPo-SE19-O7KpQt
LV Write Access read/write
LV Creation host, time Centos7-VM-1, 2022-06-14 16:00:07 +0800
LV snapshot status source of
SNAP [INACTIVE]
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 253:2
--- Logical volume ---
LV Path /dev/storage/SNAP
LV Name SNAP
VG Name storage
LV UUID u767o6-unbb-ODfU-bVA1-cF03-P9kN-3pVgkY
LV Write Access read/write
LV Creation host, time Centos7-VM-1, 2022-06-15 10:35:22 +0800
LV snapshot status INACTIVE destination for vo
LV Status available
# open 0
LV Size 2.00 GiB
Current LE 512
COW-table size 120.00 MiB
COW-table LE 30
Snapshot chunk size 4.00 KiB
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:5
[root@Centos7-VM-1 ~]# umount /mnt/vo
[root@Centos7-VM-1 ~]# lvconvert --merge /dev/storage/SNAP
Unable to merge invalidated snapshot LV storage/SNAP.
# 记得删除快照，以便后续操作
[root@Centos7-VM-1 ~]# lvremove /dev/storage/SNAP
Do you really want to remove active logical volume storage/SNAP? [y/n]: y
Logical volume "SNAP" successfully removed
删除逻辑卷
第1步：取消逻辑卷与目录的挂载关联，删除配置文件中永久生效的设备参数。
[root@localhost ~]# umount /mnt/vo/
[root@localhost ~]# vi /etc/fstab
#
# /etc/fstab
# Created by anaconda on Mon Apr 15 17:31:00 2019
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
/dev/mapper/centos-root / xfs defaults 0 0
UUID=63e91158-e754-41c3-b35d-7b9698e71355 /boot xfs defaults 0 0
/dev/mapper/centos-swap swap swap defaults 0 0
第2步：删除逻辑卷设备，需要输入y来确认操作
[root@localhost ~]# lvremove /dev/storage/vo
Do you really want to remove active logical volume storage/vo? [y/n]: y
Logical volume "vo" successfully removed
第3步：删除卷组，此处只写卷组名称即可，不需要设备的绝对路径。
[root@localhost ~]# vgremove storage
Volume group "storage" successfully removed
第4步：删除物理卷设备
[root@localhost ~]# pvremove /dev/sdb /dev/sdc
Labels on physical volume "/dev/sdb" successfully wiped.
Labels on physical volume "/dev/sdc" successfully wiped.