大纲

一、简介

二、版本

三、LVM 模块

四、具体操作

  • 对添加的硬盘进行分区(fdisk /dev/[hs]d[a-z])

  • 对创建的分区创建物理卷(pvcreate)

  • 给逻辑卷创建逻辑容器(卷组）

  • 在卷组创建大小不同的逻辑卷(lvcreate)

  • 给以存在的卷组扩大容量

  • 实现在线扩大LVM容量

  • 实现缩减LVM容量(不支持在线缩减)

  • 减小卷组容量

  • 利用给LVM创建快照，并完成备份并还原数据

一、简介

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Heinz Mauelshagen在Linux 2.4内核上实现，于1998年发布到Linux社区中，它允许你在Linux系统上用简单的命令行管理一个完整的逻辑卷管理环境。

二、版本

LVM1  最初的LVM与1998年发布，只在Linux内核2.4版本上可用，它提供最基本的逻辑卷管理。

LVM2  LVM-1的更新版本，在Linux内核2.6中才可用，它在标准的LVM-1功能外还提供了额外的功能。

查看：（测试机CentOS 5.5 X86_64）

[root@localhost ~]# uname -a  
Linux localhost.localdomain 2.6.18-194.el5 #1 SMP Fri Apr 2 14:58:14 EDT 2010 x86_64 x86_64 x86_64 GNU/Linux   
[root@localhost ~]# uname -r   
2.6.18-194.el5   
[root@localhost ~]# rpm -qa | grep lvm   
lvm2-2.02.56-8.el5   
[root@localhost ~]#

三、LVM 模块

Physical volume (PV)、Volume group (VG)、Logical volume(LV)、 Physical extent (PE)，下面我们用一个简单的图来说明下物理卷、卷组、逻辑卷他们之间的关系(此图只是个人理解，仅供参考)

LVM 详解_第1张图片

简而言之：  
逻辑卷的创建，就是将多块硬盘创建物理卷，而将这些物理卷以逻辑的形式总成一个容器，然后从这个容器里面创建大小不同的分区文件，而这个容器就是所谓的逻辑卷，而从这个容器里创建大小不同的分区文件，这个分区文件就叫做逻辑卷。嘿嘿，你懂了吗？ ^_^ ……

四、具体操作

1. 分区

[root@localhost ~]# fdisk –l #查看已存在的分区与硬盘
Disk /dev/sda: 21.4 GB, 21474836480 bytes    
255 heads, 63 sectors/track, 2610 cylinders     
Units = cylinders of 16065 * 512 = 8225280 bytes
   Device Boot      Start         End      Blocks   Id  System    
/dev/sda1   *           1          33      265041   83  Linux     
/dev/sda2              34        1308    10241437+  83  Linux     
/dev/sda3            1309        1945     5116702+  83  Linux     
/dev/sda4            1946        2610     5341612+   5  Extended     
/dev/sda5            1946        2072     1020096   82  Linux swap / Solaris
Disk /dev/sdb: 21.4 GB, 21474836480 bytes    
255 heads, 63 sectors/track, 2610 cylinders     
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdb doesn't contain a valid partition table
Disk /dev/sdc: 21.4 GB, 21474836480 bytes    
255 heads, 63 sectors/track, 2610 cylinders     
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk /dev/sdc doesn't contain a valid partition table
[root@localhost ~]# fdisk /dev/sdb #给/sdb分区,效果如下
Command (m for help): p
Disk /dev/sdb: 21.4 GB, 21474836480 bytes    
255 heads, 63 sectors/track, 2610 cylinders     
Units = cylinders of 16065 * 512 = 8225280 bytes
   Device Boot      Start         End      Blocks   Id  System    
/dev/sdb1               1         244     1959898+  8e  Linux LVM #注意修改分区类型为8e     
/dev/sdb2             245         488     1959930   8e  Linux LVM     
/dev/sdb3             489         732     1959930   8e  Linux LVM
Command (m for help):
[root@localhost ~]# partprobe #让内核重新读取一下硬盘
[root@localhost ~]# fdisk -l /dev/sdb
Disk /dev/sdb: 21.4 GB, 21474836480 bytes    
255 heads, 63 sectors/track, 2610 cylinders     
Units = cylinders of 16065 * 512 = 8225280 bytes
   Device Boot      Start         End      Blocks   Id  System    
/dev/sdb1               1         244     1959898+  8e  Linux LVM     
/dev/sdb2             245         488     1959930   8e  Linux LVM     
/dev/sdb3             489         732     1959930   8e  Linux LVM     
[root@localhost ~]#

2. 将物理分区与硬盘创建为物理卷(pvcreate)

[root@localhost ~]# pvcreate /dev/sdb[1-3] #将分区创建为物理卷    
  Physical volume "/dev/sdb1" successfully created     
  Physical volume "/dev/sdb2" successfully created     
  Physical volume "/dev/sdb3" successfully created     
[root@localhost ~]#
[root@localhost ~]# pvcreate /dev/sdc  #将硬盘创建为物理卷    
  Physical volume "/dev/sdc" successfully created
[root@localhost ~]# pvs #查看创建的物理卷    
  PV         VG   Fmt  Attr PSize  PFree      
  /dev/sdb1  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb2  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb3  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdc   myvg lvm2 a-   20.00G 20.00G

3. 将物理卷(pv)创建为卷组(vgcreate)，名为myvg

[root@localhost ~]# vgcreate myvg /dev/sdb[1-3] /dev/sdc
  Volume group "myvg" successfully created    
[root@localhost ~]# vgs     
  VG   #PV #LV #SN Attr   VSize  VFree      
  myvg   4   0   0 wz--n- 25.60G 25.60G     
[root@localhost ~]#
[root@localhost ~]# vgdisplay    
  --- Volume group ---     
  VG Name               myvg #卷组名     
  System ID            
  Format                lvm2     
  Metadata Areas        4     
  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                4     
  Act PV                4     
  VG Size               25.60 GB     
  PE Size               4.00 MB #物理盘的基本单位：默认4MB     
  Total PE              6553     
  Alloc PE / Size       0 / 0  
  Free  PE / Size       6553 / 25.60 GB     
  VG UUID               wuNBgb-tP95-pVoX-ehHw-cMfN-hyem-PNMqwe     
[root@localhost ~]#

4. 在卷组里创建逻辑卷并格式化、挂载使用

[root@localhost ~]# lvcreate -L 2G -n mylv1 myvg #创建逻辑卷    
  Logical volume "mylv1" created     
[root@localhost ~]# lvs #查看逻辑卷     
  LV    VG   Attr   LSize Origin Snap%  Move Log Copy%  Convert     
  mylv1 myvg -wi-a- 2.00G                                     
[root@localhost ~]# mke2fs -j /dev/myvg/mylv1 #格式化逻辑卷     
mke2fs 1.39 (29-May-2006)     
Filesystem label=     
OS type: Linux     
Block size=4096 (log=2)     
Fragment size=4096 (log=2)     
262144 inodes, 524288 blocks     
26214 blocks (5.00%) reserved for the super user     
First data block=0     
Maximum filesystem blocks=536870912     
16 block groups     
32768 blocks per group, 32768 fragments per group     
16384 inodes per group     
Superblock backups stored on blocks:      
        32768, 98304, 163840, 229376, 294912
Writing inode tables: done                           
Creating journal (16384 blocks): done     
Writing superblocks and filesystem accounting information: done
This filesystem will be automatically checked every 26 mounts or    
180 days, whichever comes first.  Use tune2fs -c or -i to override.     
[root@localhost ~]# mkdir /mydata #创建挂载目录     
[root@localhost ~]# mount /dev/myvg/mylv1 /mydata/ #挂载
[root@localhost ~]# mount #查看是否挂载成功    
/dev/sda2 on / type ext3 (rw)     
proc on /proc type proc (rw)     
sysfs on /sys type sysfs (rw)     
devpts on /dev/pts type devpts (rw,gid=5,mode=620)     
/dev/sda3 on /data type ext3 (rw)     
/dev/sda1 on /boot type ext3 (rw)     
tmpfs on /dev/shm type tmpfs (rw)     
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw)     
sunrpc on /var/lib/nfs/rpc_pipefs type rpc_pipefs (rw)     
/dev/mapper/myvg-mylv1 on /mydata type ext3 (rw)     
[root@localhost ~]#
[root@localhost ~]# ls /mydata/ #查看    
lost+found     
[root@localhost ~]# df –h #查看硬盘     
Filesystem            Size  Used Avail Use% Mounted on     
/dev/sda2             9.5G  1.8G  7.2G  20% /     
/dev/sda3             4.8G  138M  4.4G   4% /data     
/dev/sda1             251M   17M  222M   7% /boot     
tmpfs                  60M     0   60M   0% /dev/shm     
/dev/mapper/myvg-mylv1     
                      2.0G   68M  1.9G   4% /mydata     
[root@localhost ~]#

5. 发现卷组空间不够，我们扩大卷组空间     

[root@localhost ~]# pvcreate /dev/sdd #将新硬盘/sdd加入物理卷中     
  Physical volume "/dev/sdd" successfully created
[root@localhost ~]# pvs #查看物理卷    
  /dev/cdrom: open failed: No medium found     
  PV         VG   Fmt  Attr PSize  PFree      
  /dev/sdb1  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb2  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb3  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdc   myvg lvm2 a-   20.00G 18.00G     
  /dev/sdd   myvg lvm2 a-   20.00G 20.00G     
[root@localhost ~]#
[root@localhost ~]# vgextend myvg /dev/sdd #扩展卷组    
  Volume group "myvg" successfully extended     
[root@localhost ~]# vgs #查看新增加的卷组     
    VG   #PV #LV #SN Attr   VSize  VFree      
  myvg   5   1   0 wz--n- 45.59G 43.59G     
[root@localhost ~]#

6. 扩展逻辑卷 (支持在线扩展) 

将/dev/myvg/mylv1 扩展到4G，并且要求数据可以正常访问
[root@localhost ~]# cd /mydata/    
[root@localhost mydata]# touch index.html     
[root@localhost mydata]# echo "test" > index.html      
[root@localhost mydata]# cat index.html      
test
[root@localhost mydata]# vgs    
  /dev/cdrom: open failed: No medium found     
  VG   #PV #LV #SN Attr   VSize  VFree      
  myvg   5   1   0 wz--n- 45.59G 43.59G     
[root@localhost mydata]# lvextend -L +2G /dev/myvg/mylv1 
   Extending logical volume mylv1 to 4.00 GB     
  Logical volume mylv1 successfully resized
[root@localhost mydata]# resize2fs -p /dev/myvg/mylv1 #通过 resize2fs 将文件系统的容量确实添加
resize2fs 1.39 (29-May-2006)     
Filesystem at /dev/myvg/mylv1 is mounted on /mydata; on-line resizing required     
Performing an on-line resize of /dev/myvg/mylv1 to 1048576 (4k) blocks.     
The filesystem on /dev/myvg/mylv1 is now 1048576 blocks long.
[root@localhost mydata]# lvs    
  LV    VG   Attr   LSize Origin Snap%  Move Log Copy%  Convert     
  mylv1 myvg -wi-ao 4.00G                                     
[root@localhost mydata]#
[root@localhost mydata]# cat index.html     
test     
[root@localhost mydata]# df -h     
Filesystem            Size  Used Avail Use% Mounted on     
/dev/sda2             9.5G  1.8G  7.2G  20% /     
/dev/sda3             4.8G  138M  4.4G   4% /data     
/dev/sda1             251M   17M  222M   7% /boot     
tmpfs                  60M     0   60M   0% /dev/shm     
/dev/mapper/myvg-mylv1     
                      4.0G   69M  3.7G   2% /mydata #成功增加了2G     
[root@localhost mydata]#

7. 缩减逻辑卷

  • 查看逻辑卷使用空间状况

  • 不能在线缩减，得先卸载

  • 确保缩减后的空间大小依然能存储原有的所有数据

  • 在缩减之前应该先强行检查文件，以确保文件系统处于一至性状态


将/dev/myvg/mylv1 缩减到1G，并且要求数据可以正常访问 (所以我们就按上面的提示在操作）
[root@localhost ~]#df –lh #查看已用空间大小
[root@localhost ~]# umount /dev/myvg/mylv1 #卸载分区
[root@localhost ~]# e2fsck -f /dev/myvg/mylv1 #强制检查文件系统
[root@localhost ~]# resize2fs /dev/myvg/mylv1 1G #缩减逻辑大小     
[root@localhost ~]# lvreduce -L 1G /dev/myvg/mylv1 #缩减物理边界大小
[root@localhost ~]# lvs #查看逻辑卷    
  /dev/cdrom: open failed: No medium found     
  LV    VG   Attr   LSize Origin Snap%  Move Log Copy%  Convert     
  mylv1 myvg -wi-ao 1.00G                                     
[root@localhost ~]# mount /dev/myvg/mylv1 /mydata
[root@localhost ~]# ls /mydata/    
index.html  lost+found     
[root@localhost ~]# cat /mydata/index.html      
test     
[root@localhost ~]#

8. 缩减磁盘空间

发现物理磁盘空间使用不足，将其中一块硬盘或分区拿掉

  • pvmove /dev/sdb1 #将/dev/sdb1上存储的数据移到其它物理卷中

  • vgreduce myvg /dev/sdb1 #将/dev/sdb1从myvg卷组中移除

  • pvremove /dev/sdb1 #将/dev/sdb1从物理卷上移除

[root@localhost ~]# pvs    
  /dev/cdrom: open failed: No medium found     
  PV         VG   Fmt  Attr PSize  PFree      
  /dev/sdb1  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb2  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb3  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdc   myvg lvm2 a-   20.00G 19.00G     
  /dev/sdd   myvg lvm2 a-   20.00G 20.00G     
[root@localhost ~]#
[root@localhost ~]# pvmove /dev/sdb1     
   No data to move for myvg
[root@localhost ~]# vgreduce myvg /dev/sdb1    
  Removed "/dev/sdb1" from volume group "myvg"
root@localhost ~]# pvremove /dev/sdb1    
  Labels on physical volume "/dev/sdb1" successfully wiped     
[root@localhost ~]# pvs     
  /dev/cdrom: open failed: No medium found     
  PV         VG   Fmt  Attr PSize  PFree      
  /dev/sdb2  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdb3  myvg lvm2 a-    1.87G  1.87G     
  /dev/sdc   myvg lvm2 a-   20.00G 19.00G     
  /dev/sdd   myvg lvm2 a-   20.00G 20.00G     
[root@localhost ~]#

9. 实现快照，进行备份还原

在/mnt/lvm目录上，我们将原始的目录文件进行快照，然后将/mydata目录中的内容清空，并进行还原

[root@localhost ~]# cd /mydata/    
[root@localhost mydata]# ls     
index.html  lost+found     
[root@localhost mydata]# cat index.html      
test     
[root@localhost mydata]# lvcreate -L 30M -n backup -s -p r /dev/myvg/mylv1 #-L 快照大小 –n:快照名称 –p 权限只读 –s 创建快照     
  Rounding up size to full physical extent 32.00 MB     
  Logical volume "backup" created     
[root@localhost mydata]# ll     
total 20     
-rw-r--r-- 1 root root     5 Jun 28 01:04 index.html     
drwx------ 2 root root 16384 Jun 28 00:47 lost+found     
[root@localhost mydata]# mkdir /tmp/backup #创建挂载目录     
[root@localhost mydata]# mount /dev/myvg/backup /tmp/backup/ #挂载
mount: block device /dev/myvg/backup is write-protected, mounting read-only    
[root@localhost mydata]# cd /tmp/backup/     
[root@localhost backup]# ls     
index.html  lost+found     
[root@localhost backup]# mkdir /tmp/lvmbackup #创建备份目录     
[root@localhost backup]# tar jcf /tmp/lvmbackup/sandy.tar.bz2 index.html  #打包并压缩文件     
[root@localhost backup]# cd ..     
[root@localhost tmp]# cd lvmbackup/     
[root@localhost lvmbackup]# ls #查看备份     
sandy.tar.bz2     
[root@localhost lvmbackup]# cd /mydata/     
[root@localhost mydata]# ll     
total 20     
-rw-r--r-- 1 root root     5 Jun 28 01:04 index.html     
drwx------ 2 root root 16384 Jun 28 00:47 lost+found     
[root@localhost mydata]# rm -rf * #删除所有文件     
[root@localhost mydata]#      
[root@localhost mydata]# ll     
total 0     
[root@localhost mydata]# tar xf /tmp/lvmbackup/sandy.tar.bz2 #还原备份数据     
[root@localhost mydata]# ll     
total 4     
-rw-r--r-- 1 root root 5 Jun 28 01:04 index.html     
[root@localhost mydata]# cat index.html      
test     
[root@localhost mydata]# df -h     
Filesystem            Size  Used Avail Use% Mounted on     
/dev/sda2             9.5G  1.8G  7.2G  21% /     
/dev/sda3             4.8G  138M  4.4G   4% /data     
/dev/sda1             251M   17M  222M   7% /boot     
tmpfs                  60M     0   60M   0% /dev/shm     
/dev/mapper/myvg-mylv1     
                     1008M   67M  901M   7% /mydata     
/dev/mapper/myvg-mylv1     
                     1008M   67M  901M   7% /tmp/backup     
[root@localhost mydata]#

了解以上步骤操作的含义，我相信大家应该对LVM有更深的认识，嘿嘿 ^_^……