对于Linux LVM一直不太理解，直到最近使用了简单功能后才稍微明白点。
对于硬盘空间物理上的使用，我们都是先对硬盘进行分区，然后格式化成文件系统支持的类型，最后给操作系统使用。但是这种使用方式很不灵活，分完区之后如果想动态扩大或者缩小容量需要格式化硬盘后重新分区调整。LVM正好可以解决这个问题，提供一种灵活可变的硬盘空间使用方式。
LVM的基本结构如下图：
其中Disk Partition是物理硬盘分区，我们需要在每个物理分区上建立对应的PV（物理卷），Disk Partition和PV应该是一一对应的。VG是一个逻辑层，将所有PV的资源进行整合，形成一个存储池。然后可以将VG再细分为LV（逻辑卷），LV是最后提供给操作系统使用的卷。
本文将对一个已建立的LVM进行硬盘的扩容，步骤如下：
1、查看分区情况
# fdisk -l Disk /dev/sda: 966.4 GB, bytes
heads, sectors/track, cylinders
Units = cylinders of * = bytes
Sector size (logical/physical): bytes / bytes
I/O size (minimum/optimal): bytes / bytes
Disk identifier: 0x0003f3bd Device Boot Start End Blocks Id System
/dev/sda1 * Linux
Partition does not end on cylinder boundary.
/dev/sda2 8e Linux LVM
/dev/sda3 + Linux
/dev/sda4 Linux Disk /dev/mapper/vg_template-lv_root: 875.1 GB, bytes
heads, sectors/track, cylinders
Units = cylinders of * = bytes
Sector size (logical/physical): bytes / bytes
I/O size (minimum/optimal): bytes / bytes
Disk identifier: 0x00000000 Disk /dev/mapper/vg_template-lv_swap: MB, bytes
heads, sectors/track, cylinders
Units = cylinders of * = bytes
Sector size (logical/physical): bytes / bytes
I/O size (minimum/optimal): bytes / bytes
Disk identifier: 0x00000000 Disk /dev/mapper/vg_template-lv_home: 23.3 GB, bytes
heads, sectors/track, cylinders
Units = cylinders of * = bytes
Sector size (logical/physical): bytes / bytes
I/O size (minimum/optimal): bytes / bytes
Disk identifier: 0x00000000
可以看到硬盘目前966G左右，已经使用900G，我将为LVM再分配30G进去。
2、可以通过命令pvscan和pvdisplay查看目前已有的PV
# pvscan
PV /dev/sda2 VG vg_template lvm2 [79.51 GiB / free]
PV /dev/sda3 VG vg_template lvm2 [520.00 GiB / free]
PV /dev/sda4 VG vg_template lvm2 [299.99 GiB / 54.99 GiB free
Total: [899.50 GiB] / in use: [899.50 GiB] / in no VG: [
# pvdisplay
--- Physical volume ---
PV Name /dev/sda2
VG Name vg_template
PV Size 79.51 GiB / not usable 3.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE
Free PE
Allocated PE
PV UUID cf72cq-WGB1-AIdu-dUuN-NhGA-qXtL-2lIPSC --- Physical volume ---
PV Name /dev/sda3
VG Name vg_template
PV Size 520.00 GiB / not usable 3.96 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE
Free PE
Allocated PE
PV UUID os0owi-lP6g-3QXI-p3SF-OVYN-Dmwq-t4bcgq --- Physical volume ---
PV Name /dev/sda4
VG Name vg_template
PV Size 300.00 GiB / not usable 4.06 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE
Free PE
Allocated PE
PV UUID fSH2ET-c01w-pRdK-FlE1-Rf4l-kem4-Sk5keD
3、也可以通过vgdisplay查看VG中的剩余空间
# vgdisplay
--- Volume group ---
VG Name vg_template
System ID
Format lvm2
Metadata Areas
Metadata Sequence No
VG Access read/write
VG Status resizable
MAX LV
Cur LV
Open LV
Max PV
Cur PV
Act PV
VG Size 899.50 GiB
PE Size 4.00 MiB
Total PE
Alloc PE / Size / 844.51 GiB
Free PE / Size / 54.99 GiB
VG UUID YjcKe2-688m-1Iar-Zpa6-vbE7-TuXf-A1sgvh
可以看到，VG中海油54G左右的空间
4、查看目前已有的LV
# lvdisplay
--- Logical volume ---
LV Path /dev/vg_template/lv_root
LV Name lv_root
VG Name vg_template
LV UUID QzjkFn-VtVG-ruvw-Mpr4-UpjH-Mjpf-e6TSdK
LV Write Access read/write
LV Creation host, time Template, -- :: +
LV Status available
# open
LV Size 815.00 GiB
Current LE
Segments
Allocation inherit
Read ahead sectors auto
- currently set to
Block device : --- Logical volume ---
LV Path /dev/vg_template/lv_home
LV Name lv_home
VG Name vg_template
LV UUID PSnzWl-xeGd-aKP9-EmNL-8vxK-sMIn-z6KMDE
LV Write Access read/write
LV Creation host, time Template, -- :: +
LV Status available
# open
LV Size 21.68 GiB
Current LE
Segments
Allocation inherit
Read ahead sectors auto
- currently set to
Block device : --- Logical volume ---
LV Path /dev/vg_template/lv_swap
LV Name lv_swap
VG Name vg_template
LV UUID z4oFd5-IvA9-Y0EY-KcC1-oaOr-QZEF-7IAZSl
LV Write Access read/write
LV Creation host, time Template, -- :: +
LV Status available
# open
LV Size 7.83 GiB
Current LE
Segments
Allocation inherit
Read ahead sectors auto
- currently set to
Block device :
此次将给lv_root增加容量
5、增加LV容量
# lvextend -L +30G /dev/vg_template/lv_root
Extending logical volume lv_root to 845.00 GiB
Logical volume lv_root successfully resized
6、查看增加后的LV容量
# lvdisplay /dev/vg_template/lv_root --- Logical volume ---
LV Path /dev/vg_template/lv_root
LV Name lv_root
VG Name vg_template
LV UUID QzjkFn-VtVG-ruvw-Mpr4-UpjH-Mjpf-e6TSdK
LV Write Access read/write
LV Creation host, time Template, -- :: +
LV Status available
# open
LV Size 845.00 GiB
Current LE
Segments
Allocation inherit
Read ahead sectors auto
- currently set to
Block device :
可以看到容量从815增加至845G
7、通过df查看磁盘空间
# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_template-lv_root
803G 732G 30G % /
tmpfs 32G 25G .7G % /dev/shm
/dev/sda1 485M 38M 423M % /boot
/dev/mapper/vg_template-lv_home
22G 559M 20G % /home
发现操作系统层面看，使用空间没有变。
8、通过resize2fs重新扫描使用空间
# resize2fs /dev/vg_template/lv_root
resize2fs 1.41. (-May-)
Filesystem at /dev/vg_template/lv_root is mounted on /; on-line resizing required
old desc_blocks = , new_desc_blocks =
Performing an on-line resize of /dev/vg_template/lv_root to (4k) blocks.
The filesystem on /dev/vg_template/lv_root is now blocks long.
9、再通过df查看使用空间，空间已经扩大
]# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/vg_template-lv_root
832G 732G 58G % /
tmpfs 32G 25G .7G % /dev/shm
/dev/sda1 485M 38M 423M % /boot
/dev/mapper/vg_template-lv_home
22G 559M 20G % /home
以后继续补充如何将新加硬盘如何操作。
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以上是针对VG有剩余空间直接扩充LV的过程，下面介绍一下对于新加物理硬盘如何加到VG中。
1、查看新建物理磁盘情况
fdisk -l
Disk /dev/sdb: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
可以看到有一个200G左右的磁盘—/dev/sdb
2、对/dev/sdb进行分区
fdisk /dev/sdb
]# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x94b29f79.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help):
输入n，新建分区，根据实际情况选择主分区或者扩展分区，这里我选择主分区
Command (m for help): n
Command action
e extended
p primary partition (-)
p
Partition number (-):
First cylinder (-, default ):
Using default value
Last cylinder, +cylinders or +size{K,M,G} (-, default ):
Using default value Command (m for help):
输入t，确定分区格式，8e代表Linux LVM
Command (m for help): t
Selected partition
Hex code (type L to list codes): 8e
Changed system type of partition to 8e (Linux LVM)
输入p，查看分区状况，输入w，保存分区配置
Command (m for help): p Disk /dev/sdb: 214.7 GB, bytes
heads, sectors/track, cylinders
Units = cylinders of * = bytes
Sector size (logical/physical): bytes / bytes
I/O size (minimum/optimal): bytes / bytes
Disk identifier: 0x94b29f79 Device Boot Start End Blocks Id System
/dev/sdb1 + 8e Linux LVM Command (m for help): w
The partition table has been altered! Calling ioctl() to re-read partition table.
Syncing disks.
3、新建PV
# pvcreate /dev/sdb1
Physical volume "/dev/sdb1" successfully created
4、将新建PV加到VG中
# vgdisplay
--- Volume group ---
VG Name vg_template
System ID
Format lvm2
Metadata Areas
Metadata Sequence No
VG Access read/write
VG Status resizable
MAX LV
Cur LV
Open LV
Max PV
Cur PV
Act PV
VG Size 899.50 GiB
PE Size 4.00 MiB
Total PE
Alloc PE / Size / 874.51 GiB
Free PE / Size / 24.99 GiB
VG UUID YjcKe2-688m-1Iar-Zpa6-vbE7-TuXf-A1sgvh [root@SICS-MIGPC-DB ~]# vgextend vg_template /dev/sdb1
Volume group "vg_template" successfully extended
[root@SICS-MIGPC-DB ~]# vgdisplay
--- Volume group ---
VG Name vg_template
System ID
Format lvm2
Metadata Areas
Metadata Sequence No
VG Access read/write
VG Status resizable
MAX LV
Cur LV
Open LV
Max PV
Cur PV
Act PV
VG Size 1.07 TiB
PE Size 4.00 MiB
Total PE
Alloc PE / Size / 874.51 GiB
Free PE / Size / 224.98 GiB
VG UUID YjcKe2-688m-1Iar-Zpa6-vbE7-TuXf-A1sgvh
然后根据之前步骤扩展现有LV空间即可。
=======================================================================
其他常用命令：
1、从VG新建LV，并格式化LV为特定文件系统
新建一个100G的新LV，名称为VPS
#lvcreate –L 100G –n vps /dev/vg_template;
格式化为EXT3文件系统格式
#mkfs –t ext3 /dev/vg_template/vps
2、从VG删除PV，删除硬盘上的LVM分区，去掉硬盘
#vgreduce vg_template /dev/sdb1;
#pvremove /dev/sdb1
#fdisk /dev/sdb1
输入P，输入D（删除），输入P查看，输入W，保存配置。