LVM概述
通过使用Linux的逻辑卷管理器(Logical Volume Manager, LVM)，用户可以在系统运行时动态调整文件系统的大小，把数据从一块硬盘重定位到另一块硬盘，也可以提高I/O操作的性能，以及提供冗余保护，它的快照功能允许用户对逻辑卷进行实时的备份。
对一般用户来讲，使用最多的是动态调整文件系统大小的功能。这样，你在分区时就不必为如何设置分区的大小而烦恼，只要在硬盘中预留出部分空闲空间，然后根据系统的使用情况，动态调整分区大小
LVM相关概念
1.物理卷,PV(PhysicalVolume)
物理卷可以是一整块磁盘或者是一个分区，他为LVM提供存储介质，PV与普通分区的差异是system ID为8e.
2.物理卷组,VG(VolumeGroup)
VG是由多个PV组成.
3.物理扩展块,PE(PhysicalExtend)
LVM默认使用4MB的PE块,它是LVM中最小的存储单位.LVM的VG最多有65534个PE,因此默认LVM最大256G.可以通过调整PE大小来改变VG的最大容量,PE概念与文件系统block类似.
4.逻辑卷,LV(LogicalVolume)
最终的VG会被切成LV, LV最终可以被格式化成类似分区的存储.LV的大小需要时PE的整数倍.
LVM实现流程
通过规划PV,VG,LV之后,就可以利用mkfs格式化工具把LV变成可使用的文件系统,并且该文件系统可以在将来进行扩充或者缩减.
LVM使用的简单演示
1.使用fdisk工具创建4个分区大小均为1G,systemID为8e,分别为/dev/vdb5,/dev/vdb6,/dev/vdb7,/dev/vdb8
Disk /dev/vdb: 32.2 GB, 32212254720 bytes 16 heads, 63 sectors/track, 62415 cylinders Units = cylinders of 1008 * 512 = 516096 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disk identifier: 0x5d9b384e Device Boot Start End Blocks Id System /dev/vdb1 1 41611 20971912+ 83 Linux /dev/vdb2 41612 62415 10485216 5 Extended /dev/vdb5 41612 43693 1049296+ 8e Linux LVM /dev/vdb6 43694 45775 1049296+ 8e Linux LVM /dev/vdb7 45776 47857 1049296+ 8e Linux LVM /dev/vdb8 47858 49939 1049296+ 8e Linux LVM
2.使用pvcreate创建pv
几个跟pv相关的命令
- pvcreate: 将物理分区创建成pv
- pvscan: 查看pv
- pvdisplay: 查看所有pv状态
- pvmove: pv属性删除
[root@zwj ~]# pvcreate /dev/vdb{5..8}
Physical volume "/dev/vdb5" successfully created
Physical volume "/dev/vdb6" successfully created
Physical volume "/dev/vdb7" successfully created
Physical volume "/dev/vdb8" successfully created
[root@zwj ~]# pvscan
PV /dev/vdb5 lvm2 [1.00 GiB]
PV /dev/vdb6 lvm2 [1.00 GiB]
PV /dev/vdb7 lvm2 [1.00 GiB]
PV /dev/vdb8 lvm2 [1.00 GiB]
Total: 4 [4.00 GiB] / in use: 0 [0 ] / in no VG: 4 [4.00 GiB]
[root@zwj ~]#
[root@zwj ~]# pvdisplay
"/dev/vdb5" is a new physical volume of "1.00 GiB"
--- NEW Physical volume ---
PV Name /dev/vdb5
VG Name
PV Size 1.00 GiB
Allocatable NO
PE Size 0
Total PE 0
Free PE 0
Allocated PE 0
PV UUID YAtMpF-klHI-ZCUk-cZlw-Ff7C-A5KK-1zlIly
"/dev/vdb6" is a new physical volume of "1.00 GiB"
此处省略。。。/dev/vdb6,7,8
3.创建VG
vg相关命令
- vgcreate: 创建vg
- vgscan: 查看系统上的vg
- vgdisplay: 显示vg状态
- vgextend: 在vg内增加pv
- vgreduce: 在vg内删除pv
- vgchange: 设置vg是否启动
- vgremove: 删除vg
[root@zwj ~]# vgscan #创建vg前查看是否有vg Reading all physical volumes. This may take a while... [root@zwj ~]# vgcreate -s 16M mytestvg /dev/vdb{5,6,7} #先把pv /dev/vdb{5,6,7}加入vg -s参数用来设置PE大小,默认4M Volume group "mytestvg" successfully created [root@zwj ~]# vgscan #再次查看vg是否存在， Reading all physical volumes. This may take a while... Found volume group "mytestvg" using metadata type lvm2 #我们创建的名为mytestvg的vg [root@zwj ~]# vgdisplay #查看vg状态 --- Volume group --- VG Name mytestvg System ID Format lvm2 Metadata Areas 3 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 3 Act PV 3 VG Size 2.95 GiB PE Size 16.00 MiB Total PE 189 Alloc PE / Size 0 / 0 Free PE / Size 189 / 2.95 GiB VG UUID Pf6hlf-90cR-qU49-lqGX-0eW8-TIkg-Anw6M4
vg太小，把最后一个pv,/dev/vdb8加进去
[root@zwj ~]# vgextend mytestvg /dev/vdb8 Volume group "mytestvg" successfully extended [root@zwj ~]# vgdisplay mytestvg --- Volume group --- VG Name mytestvg System ID Format lvm2 Metadata Areas 4 Metadata Sequence No 2 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 3.94 GiB PE Size 16.00 MiB Total PE 252 Alloc PE / Size 0 / 0 Free PE / Size 252 / 3.94 GiB VG UUID Pf6hlf-90cR-qU49-lqGX-0eW8-TIkg-Anw6M4
4.创建LV
与lv相关命令
- lvcreate: 创建LV
- lvscan: 查看系统上的LV
- lvdisplay: 查看LV状态
- lvextend: 增加LV容量
- lvreduce: 缩小LV容量
- lvremove: 删除LV
- lvresize: 对LV大小进行调整
[root@zwj ~]# lvcreate -l 252 -n mytestlv mytestvg #-l 后面接要分配给LV的个数，这里把全部252个PE都给了mytestlv，-n 接lv名字 Logical volume "mytestlv" created. [root@zwj ~]# lvscan ACTIVE '/dev/mytestvg/mytestlv' [3.94 GiB] inherit #lv信息 [root@zwj ~]# lvdisplay #lv状态 --- Logical volume --- LV Path /dev/mytestvg/mytestlv #逻辑卷路径,也是全名，必须写全，不可以只写mytestlv LV Name mytestlv VG Name mytestvg LV UUID KiWyMs-Ia9T-O06E-dWRb-wcQ6-P1Ph-kYN0HK LV Write Access read/write LV Creation host, time zwj, 2017-05-06 18:10:11 +0800 LV Status available # open 0 LV Size 3.94 GiB Current LE 252 Segments 4 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:1 [root@zwj ~]#
[root@zwj ~]# ls -l /dev/mytestvg/mytestlv
lrwxrwxrwx 1 root root 7 May 6 18:10 /dev/mytestvg/mytestlv -> ../dm-1
5.格式化为文件系统
[root@zwj ~]# mkfs.ext3 /dev/mytestvg/mytestlv mke2fs 1.41.12 (17-May-2010) Filesystem label= OS type: Linux Block size=4096 (log=2) Fragment size=4096 (log=2) Stride=0 blocks, Stripe width=0 blocks 258048 inodes, 1032192 blocks 51609 blocks (5.00%) reserved for the super user First data block=0 Maximum filesystem blocks=1056964608 32 block groups 32768 blocks per group, 32768 fragments per group 8064 inodes per group Superblock backups stored on blocks: 32768, 98304, 163840, 229376, 294912, 819200, 884736 Writing inode tables: done Creating journal (16384 blocks): done Writing superblocks and filesystem accounting information: done This filesystem will be automatically checked every 21 mounts or 180 days, whichever comes first. Use tune2fs -c or -i to override. [root@zwj ~]# mkdir /mnt/lvm [root@zwj ~]# mount /dev/mytestvg/mytestlv /mnt/lvm/ [root@zwj ~]# mount /dev/vda1 on / type ext3 (rw,noatime,acl,user_xattr) proc on /proc type proc (rw) sysfs on /sys type sysfs (rw) devpts on /dev/pts type devpts (rw,mode=0620,gid=5) /dev/vdb1 on /mydata type ext3 (rw) none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw) /dev/mapper/mytestvg-mytestlv on /mnt/lvm type ext3 (rw) [root@zwj ~]#
6.扩展LV容量
- 使用fdisk创建新的SystemID=8e的分区/dev/vdb9
- 使用pvcreate创建新的PV
- 使用vgextend加入新的PV
- 使用lvresize京vg新加入的PE加入LV
- 使用resize2fs增加文件系统容量
[root@zwj ~]# pvscan PV /dev/vdb5 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb6 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb7 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb8 VG mytestvg lvm2 [1008.00 MiB / 0 free] Total: 4 [3.94 GiB] / in use: 4 [3.94 GiB] / in no VG: 0 [0 ] [root@zwj ~]# pvcreate /dev/vdb9 Physical volume "/dev/vdb9" successfully created [root@zwj ~]# pvscan PV /dev/vdb5 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb6 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb7 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb8 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb9 lvm2 [1.00 GiB] Total: 5 [4.94 GiB] / in use: 4 [3.94 GiB] / in no VG: 1 [1.00 GiB] [root@zwj ~]# vgextend mytestvg /dev/vdb9 Volume group "mytestvg" successfully extended [root@zwj ~]# vgdisplay mytestvg --- Volume group --- VG Name mytestvg System ID Format lvm2 Metadata Areas 5 Metadata Sequence No 4 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 0 Max PV 0 Cur PV 5 Act PV 5 VG Size 4.92 GiB PE Size 16.00 MiB Total PE 315 Alloc PE / Size 252 / 3.94 GiB Free PE / Size 63 / 1008.00 MiB VG UUID Pf6hlf-90cR-qU49-lqGX-0eW8-TIkg-Anw6M4 [root@zwj ~]# lvresize -l +63 /dev/mytestvg/mytestlv Size of logical volume mytestvg/mytestlv changed from 3.94 GiB (252 extents) to 4.92 GiB (315 extents). Logical volume mytestlv successfully resized. [root@zwj ~]# lvdisplay --- Logical volume --- LV Path /dev/mytestvg/mytestlv LV Name mytestlv VG Name mytestvg LV UUID KiWyMs-Ia9T-O06E-dWRb-wcQ6-P1Ph-kYN0HK LV Write Access read/write LV Creation host, time zwj, 2017-05-06 18:10:11 +0800 LV Status available # open 0 LV Size 4.92 GiB Current LE 315 Segments 5 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 [root@zwj ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/vda1 20G 13G 5.9G 69% / /dev/vdb1 20G 936M 18G 5% /mydata /dev/mapper/mytestvg-mytestlv 3.9G 80M 3.7G 3% /mnt/lvm [root@zwj ~]# resize2fs /dev/mytestvg/mytestlv resize2fs 1.41.12 (17-May-2010) Filesystem at /dev/mytestvg/mytestlv is mounted on /mnt/lvm; on-line resizing required old desc_blocks = 1, new_desc_blocks = 1 Performing an on-line resize of /dev/mytestvg/mytestlv to 1290240 (4k) blocks. The filesystem on /dev/mytestvg/mytestlv is now 1290240 blocks long. [root@zwj ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/vda1 20G 13G 5.9G 69% / /dev/vdb1 20G 936M 18G 5% /mydata /dev/mapper/mytestvg-mytestlv 4.9G 80M 4.6G 2% /mnt/lvm #扩展成功 [root@zwj ~]# ls -l /mnt/lvm/ total 20 drwx------ 2 root root 16384 May 6 18:15 lost+found drwxr-xr-x 4 weelin weelin 4096 May 6 18:18 test
7.缩小LV容量（假设要把/dev/vdb5解放出来)
- 使用resize2fs把文件系统大小设定为去除/dev/vdb5后的容量
- 使用lvresize从LV中减去对应PE数目
- 使用vgreduce把/dev/vdb5移出mytestvg, (前提要视情况使用pvmove把/dev/vdb5中的PE移到空闲的PV)
- 使用pvremove去掉/dev/vdb5的PV属性
[root@zwj ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/vda1 20G 13G 5.9G 69% / /dev/vdb1 20G 936M 18G 5% /mydata /dev/mapper/mytestvg-mytestlv 4.9G 80M 4.6G 2% /mnt/lvm [root@zwj ~]# resize2fs /dev/mytestvg/mytestlv 4096M #缩小文件系统 resize2fs 1.41.12 (17-May-2010) Filesystem at /dev/mytestvg/mytestlv is mounted on /mnt/lvm; on-line resizing required On-line shrinking from 1290240 to 1048576 not supported. [root@zwj ~]# umount /dev/mytestvg/mytestlv #需要离线搞 [root@zwj ~]# resize2fs /dev/mytestvg/mytestlv 4096M resize2fs 1.41.12 (17-May-2010) Please run 'e2fsck -f /dev/mytestvg/mytestlv' first. [root@zwj ~]# e2fsck -f /dev/mytestvg/mytestlv #检查卷 e2fsck 1.41.12 (17-May-2010) 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/mytestvg/mytestlv: 187/322560 files (0.0% non-contiguous), 40486/1290240 blocks [root@zwj ~]# resize2fs /dev/mytestvg/mytestlv 4096M #缩小文件系统 resize2fs 1.41.12 (17-May-2010) Resizing the filesystem on /dev/mytestvg/mytestlv to 1048576 (4k) blocks. The filesystem on /dev/mytestvg/mytestlv is now 1048576 blocks long. [root@zwj ~]# lvresize -l -64 /dev/mytestvg/mytestlv #缩小LV，通过减少PE方式 WARNING: Reducing active logical volume to 3.92 GiB. THIS MAY DESTROY YOUR DATA (filesystem etc.) Do you really want to reduce mytestvg/mytestlv? [y/n]: y Size of logical volume mytestvg/mytestlv changed from 4.92 GiB (315 extents) to 3.92 GiB (251 extents). Logical volume mytestlv successfully resized. [root@zwj ~]# lvdisplay --- Logical volume --- LV Path /dev/mytestvg/mytestlv LV Name mytestlv VG Name mytestvg LV UUID KiWyMs-Ia9T-O06E-dWRb-wcQ6-P1Ph-kYN0HK LV Write Access read/write LV Creation host, time zwj, 2017-05-06 18:10:11 +0800 LV Status available # open 0 LV Size 3.92 GiB #已经少了1G Current LE 251 Segments 4 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 [root@zwj ~]# pvmove /dev/vdb5 /dev/vdb9 #这里很关键，虽然lv通过移除PE缩小了，但是/dev/vdb5的PE依然被数据占用，所以要把/dev/vdb5的PE移到空闲的PE中 /dev/vdb5: Moved: 1.6% /dev/vdb5: Moved: 100.0% [root@zwj ~]# pvscan #/dev/vdb5的PE已经没有在使用中 PV /dev/vdb5 VG mytestvg lvm2 [1008.00 MiB / 1008.00 MiB free] PV /dev/vdb6 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb7 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb8 VG mytestvg lvm2 [1008.00 MiB / 16.00 MiB free] PV /dev/vdb9 VG mytestvg lvm2 [1008.00 MiB / 0 free] Total: 5 [4.92 GiB] / in use: 5 [4.92 GiB] / in no VG: 0 [0 ] [root@zwj ~]# vgreduce mytestvg /dev/vdb5 #从vg中移除PV Removed "/dev/vdb5" from volume group "mytestvg" [root@zwj ~]# pvscan PV /dev/vdb6 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb7 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb8 VG mytestvg lvm2 [1008.00 MiB / 16.00 MiB free] PV /dev/vdb9 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb5 lvm2 [1.00 GiB] Total: 5 [4.94 GiB] / in use: 4 [3.94 GiB] / in no VG: 1 [1.00 GiB] [root@zwj ~]# [root@zwj ~]# pvremove /dev/vdb5 #把/dev/vdb5从PV家族开除 Labels on physical volume "/dev/vdb5" successfully wiped [root@zwj ~]# pvscan PV /dev/vdb6 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb7 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb8 VG mytestvg lvm2 [1008.00 MiB / 16.00 MiB free] PV /dev/vdb9 VG mytestvg lvm2 [1008.00 MiB / 0 free] Total: 4 [3.94 GiB] / in use: 4 [3.94 GiB] / in no VG: 0 [0 ] [root@zwj ~]# mount /dev/mytestvg/mytestlv /mnt/lvm/ #重新挂载 [root@zwj ~]# df -h Filesystem Size Used Avail Use% Mounted on /dev/vda1 20G 13G 5.9G 69% / /dev/vdb1 20G 936M 18G 5% /mydata /dev/mapper/mytestvg-mytestlv 4.0G 80M 3.7G 3% /mnt/lvm #容量缩小成功 [root@zwj ~]# ls -l /mnt/lvm/ total 20 drwx------ 2 root root 16384 May 6 18:15 lost+found drwxr-xr-x 4 weelin weelin 4096 May 6 18:18 test
LVM系统快照
LVM有一个非常使用和重要的功能就是系统快照，所谓快照就是某一时刻系统的信息，快照可以用来恢复系统最初的状态.另外系统快照并不是把某一时刻的系统信息复制了一份，而只是把被改变的内容存到了快照区，未改变部分作为公用，所以并不会浪费太多的存储空间(这里非常类似来自相同docker镜像的容器共用一个image).
想要使用LVM快照功能必须要创建快照区，用来存储被改变的部分.大小可以不用太大,但是要根据实际情况.
[root@zwj lvm]# pvcreate /dev/vdb5 #搞一个PV Physical volume "/dev/vdb5" successfully created [root@zwj lvm]# pvscan PV /dev/vdb6 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb7 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb8 VG mytestvg lvm2 [1008.00 MiB / 16.00 MiB free] PV /dev/vdb9 VG mytestvg lvm2 [1008.00 MiB / 0 free] PV /dev/vdb5 lvm2 [1.00 GiB] Total: 5 [4.94 GiB] / in use: 4 [3.94 GiB] / in no VG: 1 [1.00 GiB] [root@zwj lvm]# vgextend mytestvg /dev/vdb5 Volume group "mytestvg" successfully extended [root@zwj lvm]# vgscan Reading all physical volumes. This may take a while... Found volume group "mytestvg" using metadata type lvm2 [root@zwj lvm]# vgdisplay --- Volume group --- VG Name mytestvg System ID Format lvm2 Metadata Areas 5 Metadata Sequence No 21 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 1 Max PV 0 Cur PV 5 Act PV 5 VG Size 4.92 GiB PE Size 16.00 MiB Total PE 315 Alloc PE / Size 251 / 3.92 GiB Free PE / Size 64 / 1.00 GiB VG UUID Pf6hlf-90cR-qU49-lqGX-0eW8-TIkg-Anw6M4 [root@zwj lvm]# lvcreate -l 64 -s -n mytestsnap /dev/mytestvg/mytestlv #创建/dev/mytestvg/myetest/mytestlv快照 -s表示快照 Logical volume "mytestsnap" created. [root@zwj lvm]# lvdisplay --- Logical volume --- LV Path /dev/mytestvg/mytestlv LV Name mytestlv VG Name mytestvg LV UUID KiWyMs-Ia9T-O06E-dWRb-wcQ6-P1Ph-kYN0HK LV Write Access read/write LV Creation host, time zwj, 2017-05-06 18:10:11 +0800 LV snapshot status source of mytestsnap [active] LV Status available # open 1 LV Size 3.92 GiB Current LE 251 Segments 4 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 --- Logical volume --- LV Path /dev/mytestvg/mytestsnap LV Name mytestsnap VG Name mytestvg LV UUID ObobTa-rm3b-gfr9-EaQZ-XZsP-hJvM-PDbBNN LV Write Access read/write LV Creation host, time zwj, 2017-05-06 21:20:36 +0800 LV snapshot status active destination for mytestlv LV Status available # open 0 LV Size 3.92 GiB Current LE 251 COW-table size 1.00 GiB COW-table LE 64 Allocated to snapshot 0.00% #表示快照已经使用了多少存储,变更越多，占用存储越多 Snapshot chunk size 4.00 KiB Segments 2 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:4 [root@zwj lvm]# mkdir -p /mnt/snapshot [root@zwj lvm]# mount /dev/mytestvg/mytestsnap /mnt/snapshot/ [root@zwj lvm]# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/vda1 20641404 13441536 6151352 69% / /dev/vdb1 20641788 958272 18634924 5% /mydata /dev/mapper/mytestvg-mytestlv 4129472 80920 3841516 3% /mnt/lvm #刚挂载时刻，完全相同 /dev/mapper/mytestvg-mytestsnap 4129472 80920 3841516 3% /mnt/snapshot [root@zwj lvm]# cp -a /etc /mnt/lvm/ #改变一下/mnt/lvm内容 [root@zwj lvm]# df Filesystem 1K-blocks Used Available Use% Mounted on /dev/vda1 20641404 13441536 6151352 69% / /dev/vdb1 20641788 958272 18634924 5% /mydata /dev/mapper/mytestvg-mytestlv 4129472 123644 3798792 4% /mnt/lvm /dev/mapper/mytestvg-mytestsnap 4129472 80920 3841516 3% /mnt/snapshot [root@zwj lvm]# lvdisplay --- Logical volume --- LV Path /dev/mytestvg/mytestlv LV Name mytestlv VG Name mytestvg LV UUID KiWyMs-Ia9T-O06E-dWRb-wcQ6-P1Ph-kYN0HK LV Write Access read/write LV Creation host, time zwj, 2017-05-06 18:10:11 +0800 LV snapshot status source of mytestsnap [active] LV Status available # open 1 LV Size 3.92 GiB Current LE 251 Segments 4 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:0 --- Logical volume --- LV Path /dev/mytestvg/mytestsnap LV Name mytestsnap VG Name mytestvg LV UUID ObobTa-rm3b-gfr9-EaQZ-XZsP-hJvM-PDbBNN LV Write Access read/write LV Creation host, time zwj, 2017-05-06 21:20:36 +0800 LV snapshot status active destination for mytestlv LV Status available # open 1 LV Size 3.92 GiB Current LE 251 COW-table size 1.00 GiB COW-table LE 64 Allocated to snapshot 4.15% #快照区已经记录了变更，随时可以恢复 Snapshot chunk size 4.00 KiB Segments 2 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:4
[root@zwj lvm]# ll /mnt/snapshot/
total 20
drwx------ 2 root root 16384 May 6 18:15 lost+found
drwxr-xr-x 4 weelin weelin 4096 May 6 19:12 test
[root@zwj lvm]# ll /mnt/lvm/
total 24
drwxr-xr-x. 94 root root 4096 May 6 21:21 etc
drwx------ 2 root root 16384 May 6 18:15 lost+found
drwxr-xr-x 4 weelin weelin 4096 May 6 19:12 test
[root@zwj lvm]#
当/mnt/lvm想要恢复为最开始建立快照时刻的状态时，可以进入/mnt/snapshot，然后打包备份里面的内容，这时 /dev/mytestvg/mytestsnap就可以卸载并删除了，之后格式化/dev/mytestvg/mytestlv，之后重新挂载到/mnt/lvm,之后把之前备份的内容解压到此处:
- tar -czvf /mnt/backups/lvm.tar.gz /mnt/snapshot/*
- umount /mnt/snapshot
- lvremove /dev/mytestvg/mytestsnap
- umount /mnt/lvm
- mkfs.ext3 /dev/mytestvg/mytestlv
- mount /dev/mytestvg/mytestlv /mnt/lvm
- tar -zxvf /mnt/backups/lvm.tar.gz -C /mnt/lvm
恢复完毕.