LVM逻辑卷镜像实现方法
本文演示了在CentOS5系统中实现LVM逻辑卷镜像的方法。LVM的镜像功能,有点儿类似于Raid1,即多块儿磁盘互相同步,确保资料不会丢失。
创建物理卷,卷组的步骤这里就先省略了,网上大把的教程。本文的过程如下:
1,创建4个物理卷/dev/sda1、/dev/sda2、/dev/sda3、/dev/sda4,并且将sda1-sda3三个物理卷加入到卷组vg1中,并在卷组vg1中创建包含镜像功能的逻辑卷lv1;
2,使用dd命令对物理卷sda2进行破坏,然后从卷组中发现sda2挂了,但确认文件读取正常;
3,(在不解除挂载的情况下)去除坏掉的物理卷sda2,向卷组中加入新的物理卷sda4代替之;
4,确认LVM镜像功能正常,以及文件读取正常。
创建一个包含镜像功能的逻辑卷(命名为lv1):
[root@OS ~]# lvcreate -L 3G -m1 -n lv1 vg1 /dev/sda1 /dev/sda2 /dev/sda3 Logical volume "lv1" created [root@OS ~]# lvs -a -o +devices LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices lv1 vg1 mwi-a- 3.00G lv1_mlog 5.34 lv1_mimage_0(0),lv1_mimage_1(0) [lv1_mimage_0] vg1 Iwi-ao 3.00G /dev/sda3(0) [lv1_mimage_1] vg1 Iwi-ao 3.00G /dev/sda2(0) [lv1_mlog] vg1 lwi-ao 4.00M /dev/sda1(0) |
LVM镜像需要用到-m1参数,从上面可以看出,/dev/sda2和/dev/sda3互为镜像,而/dev/sda1作为日志存储之用。
在逻辑卷上创建一个文件:
[root@OS ~]# mkfs.ext3 /dev/vg1/lv1 …… [root@OS ~]# mount /dev/vg1/lv1 /mnt/1 [root@OS ~]# echo "hello world" > /mnt/1/hi.txt [root@OS ~]# cat /mnt/1/hi.txt hello world |
对/dev/sda2进行破坏:
[root@OS ~]# dd if=/dev/zero of=/dev/sda2 count=10 bs=1M 10+0 records in 10+0 records out 10485760 bytes (10 MB) copied, 0.0133215 seconds, 787 MB/s |
确认/dev/sda2遭到了破坏:
[root@OS ~]# lvs -a -o +devices Couldn't find device with uuid 'ML2wV3-wBIr-eOG3-bXYp-SH1B-WBYq-JWn5K4'. Couldn't find device with uuid 'ML2wV3-wBIr-eOG3-bXYp-SH1B-WBYq-JWn5K4'. Couldn't find device with uuid 'ML2wV3-wBIr-eOG3-bXYp-SH1B-WBYq-JWn5K4'. LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices lv1 vg1 mwi-ao 3.00G lv1_mlog 100.00 lv1_mimage_0(0),lv1_mimage_1(0) [lv1_mimage_0] vg1 iwi-ao 3.00G /dev/sda3(0) [lv1_mimage_1] vg1 iwi-ao 3.00G unknown device(0) [lv1_mlog] vg1 lwi-ao 4.00M /dev/sda1(0) [root@OS ~]# lvscan Couldn't find device with uuid 'ML2wV3-wBIr-eOG3-bXYp-SH1B-WBYq-JWn5K4'. Couldn't find device with uuid 'ML2wV3-wBIr-eOG3-bXYp-SH1B-WBYq-JWn5K4'. Couldn't find device with uuid 'ML2wV3-wBIr-eOG3-bXYp-SH1B-WBYq-JWn5K4'. ACTIVE '/dev/vg1/lv1' [3.00 GB] inherit |
重新挂载逻辑卷,确认文件可以正常读取:
[root@OS ~]# umount /mnt/1 [root@OS ~]# mount /dev/vg1/lv1 /mnt/1 [root@OS ~]# cat /mnt/1/hi.txt hello world |
将卷组中坏掉的物理卷(/dev/sda2)移除:
[root@OS ~]# vgreduce --removemissing --force vg1 |
移除之后发现卷组信息中Mirrored volumes选项消失了:
[root@OS ~]# vgdisplay /dev/vg1 …… |
向卷组中加入新的物理卷(/dev/sda4):
[root@OS ~]# vgextend vg1 /dev/sda4 |
进行数据恢复(过程中无须解除逻辑卷的挂载):
[root@OS ~]# lvconvert -m1 /dev/vg1/lv1 /dev/sda1 /dev/sda3 /dev/sda4 /dev/vg1/lv1: Converted: 9.8% /dev/vg1/lv1: Converted: 19.4% /dev/vg1/lv1: Converted: 48.4% /dev/vg1/lv1: Converted: 77.6% /dev/vg1/lv1: Converted: 96.9% /dev/vg1/lv1: Converted: 100.0% Logical volume lv1 converted. [root@OS ~]# lvs -a -o +devices LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices lv1 vg1 mwi-ao 3.00G lv1_mlog 100.00 lv1_mimage_0(0),lv1_mimage_1(0) [lv1_mimage_0] vg1 iwi-ao 3.00G /dev/sda3(0) [lv1_mimage_1] vg1 iwi-ao 3.00G /dev/sda4(0) [lv1_mlog] vg1 lwi-ao 4.00M /dev/sda1(0) [root@OS ~]# cat /mnt/1/hi.txt hello world |