LVM详解
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转自:http://freeloda.blog.51cto.com/2033581/1231089
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) 
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
- 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 / SolarisDisk /dev/sdb: 21.4 GB, 21474836480 bytes 255 heads, 63 sectors/track, 2610 cylinders Units = cylinders of 16065 * 512 = 8225280 bytesDisk /dev/sdb doesn't contain a valid partition tableDisk /dev/sdc: 21.4 GB, 21474836480 bytes 255 heads, 63 sectors/track, 2610 cylinders Units = cylinders of 16065 * 512 = 8225280 bytesDisk /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): pDisk /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 LVMCommand (m for help):[root@localhost ~]# partprobe #让内核重新读取一下硬盘[root@localhost ~]# fdisk -l /dev/sdbDisk /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 20.00G3.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, 294912Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: doneThis 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]# 0 0
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