Linux LVM使用小记

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。

==================================================================================================

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。