LVM镜像

本文转自http://luyadong.blog.51cto.com/2876653/801082
1、创建lvm的镜像

fdisk /dev/sdb 建立4个磁盘分区
partprobe 
pvcreate /dev/sdb5
pvcreate /dev/sdb6
pvcreate /dev/sdb7
pvcreate /dev/sdb8
pvdisplay 
vgcreate vg0 /dev/sdb5 /dev/sdb6 /dev/sdb7
创建lvm镜像/dev/vg0/mirror
lvcreate -L 2G -m1 -n mirror vg0 /dev/sdb5 /dev/sdb6 /dev/sdb7

查看/dev/vg0/mirror的信息：
[root@bogon ~]# lvdisplay /dev/vg0/mirror
--- Logical volume ---
LV Name /dev/vg0/mirror
VG Name vg0
LV UUID kHWJ34-fKma-0hKw-8lAi-zItI-VyoE-lzxWEF
LV Write Access read/write
LV Status available
# open 1
LV Size 2.00 GiB
Current LE 512
Mirrored volumes 2
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:5

查看当前lvm中设备状态：
[root@bogon ~]# lvs -a -o +devices
LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices 
LogVol00 VolGroup00 -wi-ao 41.78g /dev/sda2(0) 
LogVol01 VolGroup00 -wi-ao 8.00g /dev/sda2(1337) 
mirror vg0 mwi-ao 2.00g mirror_mlog 100.00 mirror_mimage_0(0),mirror_mimage_1(0)
[mirror_mimage_0] vg0 iwi-ao 2.00g /dev/sdb5(0) 
[mirror_mimage_1] vg0 iwi-ao 2.00g /dev/sdb6(0) 
[mirror_mlog] vg0 lwi-ao 4.00m /dev/sdb7(0)

对新建的镜像lv进行格式化、挂载：
mkfs.ext3 /dev/vg0/mirror 
mkdir /mirror
mount /dev/vg0/mirror /mirror/

2、对镜像lvm进行破坏，破坏一块pv，看是否能正常工作，
dd if=/dev/zero of=/dev/sdb5 count=10

破坏之后可以看到镜像lv中的/dev/sdb5变成了未知：
[root@bogon ~]# lvs -a -o +devices 
Couldn't find device with uuid NnJbyv-vq42-HHeM-v7YV-2c4I-I9cl-YOc00r.
LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices 
LogVol00 VolGroup00 -wi-ao 41.78g /dev/sda2(0) 
LogVol01 VolGroup00 -wi-ao 8.00g /dev/sda2(1337) 
mirror vg0 mwi-ao 2.00g mirror_mlog 100.00 mirror_mimage_0(0),mirror_mimage_1(0)
[mirror_mimage_0] vg0 iwi-ao 2.00g unknown device(0) 
[mirror_mimage_1] vg0 iwi-ao 2.00g /dev/sdb6(0) 
[mirror_mlog] vg0 lwi-ao 4.00m /dev/sdb7(0)

[root@bogon ~]# lvscan
Couldn't find device with uuid NnJbyv-vq42-HHeM-v7YV-2c4I-I9cl-YOc00r.
ACTIVE '/dev/vg0/mirror' [2.00 GiB] inherit
ACTIVE '/dev/VolGroup00/LogVol00' [41.78 GiB] inherit
ACTIVE '/dev/VolGroup00/LogVol01' [8.00 GiB] inherit

重新对镜像lv进行挂载，发现正常。
umount /mirror/ 
mount /dev/vg0/mirror /mirror/
cd /mirror/

把坏掉的设备从vg0中移除：
vgreduce --removemissing --force vg0

移除之后发现vg0信息中Mirrored volumes选项没有了
[root@bogon ~]# vgdisplay /dev/vg0
--- Volume group ---
VG Name vg0
System ID 
Format lvm2
Metadata Areas 2
Metadata Sequence No 22
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 1
Open LV 1
Max PV 0
Cur PV 2
Act PV 2
VG Size 4.01 GiB
PE Size 4.00 MiB
Total PE 1026
Alloc PE / Size 512 / 2.00 GiB
Free PE / Size 514 / 2.01 GiB
VG UUID nwo3S4-crKr-Lgri-X7Um-qfXv-6Mxo-XXXt2N

在vg0中新加一个pv，对数据进行恢复：
vgextend vg0 /dev/sdb8
[root@bogon ~]# lvconvert -m1 /dev/vg0/mirror /dev/sdb8 /dev/sdb6 /dev/sdb7 
vg0/mirror: Converted: 0.0%
vg0/mirror: Converted: 32.0%
vg0/mirror: Converted: 64.6%
vg0/mirror: Converted: 97.7%
vg0/mirror: Converted: 100.0%
[root@bogon ~]# lvs -a -o +devices
LV VG Attr LSize Origin Snap% Move Log Copy% Convert Devices 
LogVol00 VolGroup00 -wi-ao 41.78g /dev/sda2(0) 
LogVol01 VolGroup00 -wi-ao 8.00g /dev/sda2(1337) 
mirror vg0 mwi-ao 2.00g mirror_mlog 100.00 mirror_mimage_0(0),mirror_mimage_1(0)
[mirror_mimage_0] vg0 iwi-ao 2.00g /dev/sdb6(0) 
[mirror_mimage_1] vg0 iwi-ao 2.00g /dev/sdb8(0) 
[mirror_mlog] vg0 lwi-ao 4.00m /dev/sdb7(0)

[root@bogon ~]# lvdisplay /dev/vg0/mirror 
--- Logical volume ---
LV Name /dev/vg0/mirror
VG Name vg0
LV UUID kHWJ34-fKma-0hKw-8lAi-zItI-VyoE-lzxWEF
LV Write Access read/write
LV Status available
# open 1
LV Size 2.00 GiB
Current LE 512
Mirrored volumes 2 这个选项又恢复了
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 256
Block device 253:5
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