[实验]通过LVM快照进行热备

lvm快照有两大用途,一是用来克隆虚拟机,例如做xen虚拟机时,可先新建一台完整虚拟机,假设大小为10G,然后我们可以在这台10G的虚拟机上创建1个3G的快照,接着通过这个3G的快照启动虚拟机,做完实验后,可以直接删除快照而保持原来完整虚拟机的纯净。

lvm快照的第二大用途是实时备份(moment-in-time),即为了保持系统的一致性,我们先做一个快照冻结当前系统状态,这样快照里面的内容可暂时保持不变,系统本身继续运行,通过备份快照来实现不中断服务的的备份。

本文实验基于快照的热备。

[root@station122 md]# fdisk -l /dev/sdb

Disk /dev/sdb: 107.4 GB, 107374182400 bytes
255 heads, 63 sectors/track, 13054 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: 0xbfedc746

Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               1       13055   104857568+   5  Extended
/dev/sdb5               1         131     1048576+  83  Linux
/dev/sdb6             131         262     1048576+  83  Linux
/dev/sdb7             262         392     1048576+  83  Linux
/dev/sdb8             392         523     1048576+  83  Linux
/dev/sdb9             523         653     1048576+  83  Linux
/dev/sdb10            653         784     1048576   83  Linux
/dev/sdb11            784        2089    10485760   83  Linux
[root@station122 md]# pvcreate /dev/sdb5 #创建pv
  Wiping software RAID md superblock on /dev/sdb5
  Physical volume "/dev/sdb5" successfully created
[root@station122 md]# pvs
  PV         VG       Fmt  Attr PSize  PFree
  /dev/sda2  VolGroup lvm2 a-   79.51g    0
  /dev/sdb5           lvm2 a-    1.00g 1.00g
[root@station122 md]# vgcreate vg1 /dev/sdb5 #创建vg
  Volume group "vg1" successfully created
[root@station122 md]# vgs
  VG       #PV #LV #SN Attr   VSize    VFree
  VolGroup   1   3   0 wz--n-   79.51g       0
  vg1        1   0   0 wz--n- 1020.00m 1020.00m
[root@station122 md]# lvcreate -L 20M -n lv1 vg1 #创建lv
  Logical volume "lv1" created
[root@station122 md]# lvs
  LV      VG       Attr   LSize   Origin Snap%  Move Log Copy%  Convert
  lv_home VolGroup -wi-ao  28.54g
  lv_root VolGroup -wi-ao  50.00g
  lv_swap VolGroup -wi-ao 992.00m
  lv1     vg1      -wi-a-  20.00m
[root@station122 md]# mkfs.ext3 /dev/vg1/lv1 #创建文件系统
mke2fs 1.41.12 (17-May-2010)
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
Stride=0 blocks, Stripe width=0 blocks
5136 inodes, 20480 blocks
1024 blocks (5.00%) reserved for the super user
First data block=1
Maximum filesystem blocks=20971520
3 block groups
8192 blocks per group, 8192 fragments per group
1712 inodes per group
Superblock backups stored on blocks:
        8193

Writing inode tables: done
Creating journal (1024 blocks): done
Writing superblocks and filesystem accounting information: done

This filesystem will be automatically checked every 27 mounts or
180 days, whichever comes first.  Use tune2fs -c or -i to override.
[root@station122 md]# mkdir /mnt/lv1
[root@station122 md]# mount /dev/vg1/lv1 /mnt/lv1/ #挂载文件系统
[root@station122 md]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/VolGroup-lv_root
                       50G  884M   46G   2% /
tmpfs                 120M     0  120M   0% /dev/shm
/dev/sda1             485M   29M  431M   7% /boot
/dev/mapper/VolGroup-lv_home
                       29G  172M   27G   1% /home
/dev/sr0              3.2G  3.2G     0 100% /media
/dev/mapper/vg1-lv1    20M  1.2M   18M   7% /mnt/lv1
[root@station122 lv1]# rm /mnt/lv1/* -rf
[root@station122 mnt]# cp /etc/passwd lv1/ #拷贝一个文件做测试用
[root@station122 mnt]# ll lv1/
total 2
-rw-r--r--. 1 root root 902 Jul 16 19:09 passwd
[root@station122 mnt]# lvcreate -L 5M -s -n lv1_sp /dev/vg1/lv1 #创建lvm快照
  Rounding up size to full physical extent 8.00 MiB

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