Linux之LVM篇
2024-06-16 14:25:35
一、什么是LVM？
LVM是 Logical Volume Manager（逻辑卷管理）的简写。
它是Linux环境下对磁盘分区进行管理的一种机制，它由HeinzMauelshagen在Linux 2.4内核上实现，目前最新版本为：稳定版1.0.5，开发版 1.1.0-rc2，以及LVM2开发版。Linux用户安装Linux操作系统时遇到的一个常见的难以决定的问题就是如何正确地评估各分区大小，以分配合适的硬盘空间。普通的磁盘分区管理方式在逻辑分区划分好之后就无法改变其大小，当一个逻辑分区存放不下某个文件时，这个文件因为受上层文件系统的限制，也不能跨越多个分区来存放，所以也不能同时放到别的磁盘上。而遇到出现某个分区空间耗尽时，解决的方法通常是使用符号链接，或者使用调整分区大小的工具，但这只是暂时解决办法，没有从根本上解决问题。随着Linux的逻辑卷管理功能的出现，这些问题都迎刃而解，用户在无需停机的情况下可以方便地调整各个分区大小。
二、LVM的建立。
首先，先给大家普及以下Linux中lvm中的一些常见符号及意义。
pv ##物理卷：被lv命令处理过的物理分区vg ##物理卷组：被组装到一起的物理卷pe ##实体延伸区块：PE是LVM最小的存储单位，一般为4MB大小，它是构成VG的基本单位lvm ##逻辑卷：直接使用的设备，可以增大缩减并保持原有数据不变
1、xfs文件系统的LVM管理
1）分区时定分区标签为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 0x9ee14f08.Command (m for help): n
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):
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 setCommand (m for help): n
Partition type:p primary (1 primary, 0 extended, 3 free)e extended
Select (default p):
Using default response 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): +100M
Partition 2 of type Linux and of size 100 MiB is setCommand (m for help): n
Partition type:p primary (2 primary, 0 extended, 2 free)e extended
Select (default p):
Using default response p
Partition number (3,4, default 3):
First sector (411648-20971519, default 411648):
Using default value 411648
Last sector, +sectors or +size{K,M,G} (411648-20971519, default 20971519): +100M
Partition 3 of type Linux and of size 100 MiB is setCommand (m for help): n
Partition type:p primary (3 primary, 0 extended, 1 free)e extended
Select (default e):
Using default response e
Selected partition 4
First sector (616448-20971519, default 616448):
Using default value 616448
Last sector, +sectors or +size{K,M,G} (616448-20971519, default 20971519):
Using default value 20971519
Partition 4 of type Extended and of size 9.7 GiB is setCommand (m for help): wq
The partition table has been altered!Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]#
[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
All primary partitions are in use
Adding logical partition 5
First sector (618496-20971519, default 618496):
Using default value 618496
Last sector, +sectors or +size{K,M,G} (618496-20971519, default 20971519):
Using default value 20971519
Partition 5 of type Linux and of size 9.7 GiB is setCommand (m for help): d
Partition number (1-5, default 5): 5
Partition 5 is deletedCommand (m for help): n
All primary partitions are in use
Adding logical partition 5
First sector (618496-20971519, default 618496):
Using default value 618496
Last sector, +sectors or +size{K,M,G} (618496-20971519, default 20971519): +500M
Partition 5 of type Linux and of size 500 MiB is setCommand (m for help): n
All primary partitions are in use
Adding logical partition 6
First sector (1644544-20971519, default 1644544):
Using default value 1644544
Last sector, +sectors or +size{K,M,G} (1644544-20971519, default 20971519): +500M
Partition 6 of type Linux and of size 500 MiB is setCommand (m for help): t
Partition number (1-6, default 6): 5
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'Command (m for help): t
Partition number (1-6, default 6): 6
Hex code (type L to list all codes): 8e
Changed type of partition 'Linux' to 'Linux LVM'Command (m for help): pDisk /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: 0x9ee14f08Device Boot Start End Blocks Id System
/dev/vdb1 2048 206847 102400 83 Linux
/dev/vdb2 206848 411647 102400 83 Linux
/dev/vdb3 411648 616447 102400 83 Linux
/dev/vdb4 616448 20971519 10177536 5 Extended
/dev/vdb5 618496 1642495 512000 8e Linux LVM
/dev/vdb6 1644544 2668543 512000 8e Linux LVMCommand (m for help): wq
The partition table has been altered!Calling ioctl() to re-read partition table.
2）创建物理卷
pvcreate /dev/vdb5 ##创建物理卷
pvcreate /dev/vdb6
示例：
采用以下命令监视物理卷、物理卷组、逻辑卷、以及逻辑卷挂载点的有关数据。
watch -n 1 "pvs;echo ===;vgs;echo ===;lvs;echo ===;df -h /mnt"
3）创建物理卷组
vgcreate vg0 /dev/vdb5 ##创建物理卷组
vgextend vg0 /dev/vdb6
分析：把第一块物理卷加入物理卷组时用vgcreate，之后增添物理卷组都用vgextend。
4）创建逻辑卷及挂载逻辑卷
lvcreate -L 20M -n lv0 vg0 ##创建逻辑卷
mkfs.xfs /dev/vg0/lv0 ##格式化为xfs的文件系统
mount /dev/vg0/lv0 /mnt ##挂载到mnt
测试：
[root@localhost ~]# df -H /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-lv0 18M 1.2M 17M 7% /mnt
5）如何增添逻辑卷
pvcreate /dev/vdb7 ##创建物理卷标签为8e
vgextend vg0 /dev/vdb9 ##增添物理卷组
lvextend -L 1500M /dev/vg0/lv0 ##拉伸逻辑卷为1500M
xfs_growfs /dev/vg0/lv0 ##拉伸文件系统使1500M的逻辑卷可用
示例：
[root@localhost ~]# vgcreate vg0 /dev/vdb5Volume group "vg0" successfully created
[root@localhost ~]# vgextend vg0 /dev/vdb6Volume group "vg0" successfully extended
[root@localhost ~]# lvcreate -L 20M -n lv0 vg0Logical volume "lv0" created
[root@localhost ~]# mkfs.xfs /dev/vg0/lv0
meta-data=/dev/vg0/lv0 isize=256 agcount=1, agsize=5120 blks= sectsz=512 attr=2, projid32bit=1= crc=0
data = bsize=4096 blocks=5120, 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
[root@localhost ~]# df -H /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg0-lv0 18M 1.2M 17M 7% /mnt
[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
All primary partitions are in use
Adding logical partition 7
First sector (2670592-20971519, default 2670592):
Using default value 2670592
Last sector, +sectors or +size{K,M,G} (2670592-20971519, default 20971519): +1G
Partition 7 of type Linux and of size 1 GiB is setCommand (m for help): t
Partition number (1-7, default 7):
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.WARNING: Re-reading the partition table failed with error 16: Device or resource busy.
The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.
[root@localhost ~]# partprobe
[root@localhost ~]# pvcreate /dev/vdb7Physical volume "/dev/vdb7" successfully created
[root@localhost ~]# vgextend vg0 /dev/vdb7Volume group "vg0" successfully extended
[root@localhost ~]# lvextend -L 1500M /dev/vg0/lv0 Extending logical volume lv0 to 1.46 GiBLogical volume lv0 successfully resized
[root@localhost ~]# xfs_growfs /dev/vg0/lv0
meta-data=/dev/mapper/vg0-lv0 isize=256 agcount=1, agsize=5120 blks= sectsz=512 attr=2, projid32bit=1= crc=0
data = bsize=4096 blocks=5120, 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 5120 to 384000
2、ext4文件系统的硬盘缩减及拉伸
前几步与xfs文件系统的相同就不重复介绍了。
1、创建逻辑卷，将逻辑卷格式化为ext4的文件系统。
mkfs.ext4 /dev/vg0/lv0 ##lv0格式化为ext4文件系统
2、挂载ext4文件系统的lv0到/mnt，及拉伸逻辑卷、拉伸文件系统。
mount /dev/vg0/lv0 /mnt/ ##挂载
lvextend -L 1800 /dev/vg0/lv0 ##拉伸逻辑卷
resize2fs /dev/vg0/lv0 ##拉伸ext4文件系统
3、缩减逻辑卷及文件系统
umount /mnt/ ##卸载
e2fsck -f /dev/vg0/lv0 ##检查lv0数据
resize2fs /dev/vg0/lv0 1000M ##缩减ext4文件系统
mount /dev/vg0/lv0 /mnt/ ##挂载
lvreduce -L 1000M /dev/vg0/lv0 ##缩减逻辑卷
pvmove /dev/vdb6 /dev/vdb7 ##把vdb6的数据移动到vdb7
vgreduce vg0 /dev/vdb6 ##把vdb6移除vg0物理卷组
pvremove /dev/vdb6 ##把vdb6移除物理卷
示例：
[root@localhost ~]# umount /mnt/
[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: 11/120000 files (9.1% non-contiguous), 16862/460800 blocks
[root@localhost ~]# resize2fs /dev/vg0/lv0 1000M
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/
[root@localhost ~]# lvreduce -L 1000M /dev/vg0/lv0 WARNING: Reducing active and open logical volume to 1000.00 MiBTHIS MAY DESTROY YOUR DATA (filesystem etc.)
Do you really want to reduce lv0? [y/n]: yReducing logical volume lv0 to 1000.00 MiBLogical volume lv0 successfully resized
[root@localhost ~]# pvmove /dev/vdb6 /dev/vdb7No data to move for vg0
[root@localhost ~]# vgreduce vg0 /dev/vdb6Removed "/dev/vdb6" from volume group "vg0"
[root@localhost ~]# pvremove /dev/vdb6Labels on physical volume "/dev/vdb6" successfully wiped
[root@localhost ~]#
三、创建逻辑卷快照。
lvcreate -L 50M -n /dev/vg0/lv0_snap -s /dev/vg0/lv0 ##创建逻辑卷快照
mount /dev/vg0/lv0_snap /mnt/ ##挂载快照
小测试：模拟逻辑卷快照的损坏及重新拍摄快照。
[root@localhost ~]# umount /mnt/
[root@localhost ~]# mount /dev/vg0/lv0 /mnt/
[root@localhost ~]# touch /mnt/file{1..9}
[root@localhost ~]# umount /mnt/
[root@localhost ~]# lvcreate -L 50M -n /dev/vg0/lv0_snap -s /dev/vg0/lv0Rounding up size to full physical extent 52.00 MiBLogical volume "lv0_snap" created
[root@localhost ~]# mount /dev/vg0/lv0_snap /mnt/
[root@localhost ~]# ls /mnt/*
/mnt/file1 /mnt/file3 /mnt/file5 /mnt/file7 /mnt/file9
/mnt/file2 /mnt/file4 /mnt/file6 /mnt/file8/mnt/lost+found:
[root@localhost ~]# rm -rf /mnt/*
[root@localhost ~]# ls /mnt/*
ls: cannot access /mnt/*: No such file or directory
[root@localhost ~]# umount /mnt/
[root@localhost ~]# lvremove /dev/vg0/lv0_snap
Do you really want to remove active logical volume lv0_snap? [y/n]: yLogical volume "lv0_snap" successfully removed
[root@localhost ~]# lvcreate -L 50M -n /dev/vg0/lv0_snap -s /dev/vg0/lv0Rounding up size to full physical extent 52.00 MiBLogical volume "lv0_snap" created
[root@localhost ~]# mount /dev/vg0/lv0_snap /mnt/
[root@localhost ~]# ls /mnt/*
/mnt/file1 /mnt/file3 /mnt/file5 /mnt/file7 /mnt/file9
/mnt/file2 /mnt/file4 /mnt/file6 /mnt/file8/mnt/lost+found:
[root@localhost ~]#
四、删除LVM
lvremove /dev/vg0/lv0_snap ##删除逻辑卷快照
lvremove /dev/vg0/lv0 ##删除逻辑卷
vgremove vg0 ##删除物理卷组
pvremove /dev/vdb5 ##移除物理卷
pvremove /dev/vdb7 ##移除物理卷
fdisk /dev/vdb ##删除LVM分区
partprobe ##重新加载分区表
示例：
[root@localhost ~]# umount /mnt/
[root@localhost ~]# lvremove /dev/vg0/lv0_snap
Do you really want to remove active logical volume lv0_snap? [y/n]: yLogical volume "lv0_snap" successfully removed
[root@localhost ~]# lvremove /dev/vg0/lv0
Do you really want to remove active logical volume lv0? [y/n]: yLogical volume "lv0" successfully removed
[root@localhost ~]# vgremove vg0Volume group "vg0" successfully removed
[root@localhost ~]# pvremove /dev/vdb5Labels on physical volume "/dev/vdb5" successfully wiped
[root@localhost ~]# pvremove /dev/vdb7Labels on physical volume "/dev/vdb7" successfully wiped
[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): d
Partition number (1-7, default 7): 5
Partition 5 is deletedCommand (m for help): d
Partition number (1-6, default 6): 6
Partition 6 is deletedCommand (m for help): pDisk /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: 0x9ee14f08Device Boot Start End Blocks Id System
/dev/vdb1 2048 206847 102400 83 Linux
/dev/vdb2 206848 411647 102400 83 Linux
/dev/vdb3 411648 616447 102400 83 Linux
/dev/vdb4 616448 20971519 10177536 5 Extended
/dev/vdb5 1644544 2668543 512000 8e Linux LVMCommand (m for help): d
Partition number (1-5, default 5): 5
Partition 5 is deletedCommand (m for help): pDisk /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: 0x9ee14f08Device Boot Start End Blocks Id System
/dev/vdb1 2048 206847 102400 83 Linux
/dev/vdb2 206848 411647 102400 83 Linux
/dev/vdb3 411648 616447 102400 83 Linux
/dev/vdb4 616448 20971519 10177536 5 ExtendedCommand (m for help): wq
The partition table has been altered!Calling ioctl() to re-read partition table.
Syncing disks.
[root@localhost ~]#
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