测试环境：CentOS 5.10 x64，sda 20G，sdb 1G，sdc 2G.

一、创建逻辑卷镜像关系的步骤：
1）通过pvcreate命令将linux分区处理成物理卷（PV)；
2）通过vgcreate命令将创建好的物理卷处理成卷组（Vg)；
3）通过lvcreate命令使用–m1 参数将卷若干个PV组成一个逻辑镜像卷（Lv)；
之后我们可以对镜像逻辑卷进行格式化，挂载，删除等操作。

二、创建磁盘分区

首先将sbc和sdc分区，并创建三个pv（sdb1、sdc1、sdc2），其中sdb1作为数据盘，sdc1作为镜像盘，sdc2作为日志盘，日志盘不应太小（一般10G左右）。

1）将sdb分区

    [root@Centos~]# fdisk /dev/sdb

    Devicecontains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel

    Buildinga new DOS disklabel. Changes will remain in memory only,

    until youdecide to write them. After that, of course, the previous

    contentwon‘t be recoverable.

    Warning:invalid flag 0x0000 of partition table 4 will be corrected by w(rite)

    Command(m for help): n

    Commandaction

       e  extended

       p  primary partition (1-4)

    p

    Partitionnumber (1-4): 1

    Firstcylinder (1-130, default 1):

    Usingdefault value 1

    Lastcylinder or +size or +sizeM or +sizeK (1-130, default 130): +1024M

    Command(m for help): p

    Disk/dev/sdb: 1073 MB, 1073741824 bytes

    255heads, 63 sectors/track, 130 cylinders

    Units =cylinders of 16065 * 512 = 8225280 bytes

       Device Boot      Start         End      Blocks  Id  System

    /dev/sdb1               1         125    1004031   83  Linux

    Command(m for help): w

    Thepartition table has been altered!

    Callingioctl() to re-read partition table.

    Syncingdisks.

[root@Centos ~]#

2）将sdc分区

[root@Centos ~]#fdisl /dev/sdc

bash: fdisl:command not found

[root@Centos ~]#fdisk /dev/sdc

Device containsneither a valid DOS partition table, nor Sun, SGI or OSF disklabel

Building a newDOS disklabel. Changes will remain in memory only,

until you decideto write them. After that, of course, the previous

content won‘t berecoverable.

Warning: invalidflag 0x0000 of partition table 4 will be corrected by w(rite)

Command (m forhelp): n

Command action

   e  extended

   p  primary partition (1-4)

p

Partition number(1-4): 1

First cylinder(1-261, default 1): 1

Last cylinder or+size or +sizeM or +sizeK (1-261, default 261): +1024M

Command (m forhelp): n

Command action

   e  extended

   p   primary partition (1-4)

p

Partition number(1-4): 2

First cylinder(126-261, default 126):

Using defaultvalue 126

Last cylinder or+size or +sizeM or +sizeK (126-261, default 261): +1000M

Command (m forhelp): p

Disk /dev/sdc:2147 MB, 2147483648 bytes

255 heads, 63sectors/track, 261 cylinders

Units =cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks  Id  System

/dev/sdc1               1         125    1004031   83  Linux

/dev/sdc2             126         248     987997+  83  Linux

Command (m forhelp): w

The partitiontable has been altered!

Calling ioctl()to re-read partition table.

Syncing disks.

3）重读分区表

[root@centos ~]#partprobe

如果sdb、sdc是FC、iscsi、DAS存储，且配置了多路径，则使用如下命令更新分区表，若还未更新就只能init 6 重启服务器了：

kpartx –a/dev/mapper/mpathbp1  然后 ls/dev/mapper/ 查看分区设备

4）pvcreate 创建pv 设备

[root@Centos ~]#pvcreate /dev/sdb1 /dev/sdc1 /dev/sdc2

  Writing physical volume data to disk"/dev/sdb1"

  Physical volume "/dev/sdb1"successfully created

  Writing physical volume data to disk"/dev/sdc1"

  Physical volume "/dev/sdc1"successfully created

  Writing physical volume data to disk"/dev/sdc2"

  Physical volume "/dev/sdc2"successfully created

[root@Centos ~]#

查看pv设备表：

[root@centos ~]#pvscan   （或者pvs，或者 pvdisplay查看详细信息包括pvuuid）

  PV /dev/sda2  VG VolGroup00      lvm2 [19.88 GB/ 0    free]

  PV /dev/sdb1                      lvm2 [980.50 MB]

  PV /dev/sdc1                      lvm2 [980.50 MB]

  PV /dev/sdc2                      lvm2 [964.84 MB]

  Total: 4 [22.73 GB] / in use: 1 [19.88 GB] /in no VG: 3 [2.86 GB]

[root@Centos ~]#

5）vgcreate创建 vg0物理卷组

[root@Centos ~]#vgcreate vg0 /dev/sdb1 /dev/sdc1 /dev/sdc2

  Volume group "vg0" successfullycreated

[root@Centos ~]#

三、创建LVM Mirror镜像卷

[root@Centos ~]# lvcreate -L 970M -m1 -n mirror vg0 /dev/sdb1/dev/sdc1

     Rounding up size to full physical extent972.00 MB

     Logical volume "mirror" created

[root@Centos ~]#lvdisplay /dev/vg0/mirror  查看/dev/vg0/mirror

  --- Logical volume ---

  LV Name                /dev/vg0/mirror

  VG Name                vg0

  LV UUID               vX60P8-MmjC-tNX8-w2jI-t2qt-AZnD-Rnj0IN

  LV Write Access        read/write

  LV Status              available

  # open                 0

  LV Size                972.00 MB

  Current LE             243

  Mirrored volumes       2

  Segments               1

  Allocation             inherit

  Read ahead sectors     auto

  - currently set to     256

  Block device           253:5

[root@Centos ~]#lvs -a -o +devices    查看当前LVM中设备状态

   [root@Centos ~]# mkfs.ext3 /dev/vg0/mirror   格式化lvm，创建文件系统

四、管理lvm mirror卷

1）破坏一个pv设备（sdb1），然后再查看lvs状态，发现少了一个pv设备sdb1：

[root@Centos ~]#dd if=/dev/zero of=/dev/sdb1 count=10

10+0 records in

10+0 records out

    5120 bytes (5.1 kB) copied, 0.000856 seconds, 6.0 MB/s

2）把损坏的pv从vg0卷组删除（缩小vg0卷组）：

[root@Centos ~]#vgreduce --removemissing --force vg0

    Couldn‘t find device with uuidkJc1oG-Ua0R-RDiC-KaJ5-oomD-cH9Q-2DbWQ2.

Wrote out consistent volume group vg0

[root@Centos ~]#

因为上面我们是手动破坏pv，如果是pv离线或者减少vg的pv设备，使用如下指令：

[root@Centos ~]#vgreduce vg0 /dev/sdb1

移除之后发现vg0详细信息中没有了Mirrored volumes选项

[root@Centos ~]#vgdisplay /dev/vg0

      --- Volume group ---

      VG Name               vg0

      System ID            

      Format                lvm2

      Metadata Areas        2

      Metadata Sequence No  9

      VG Access             read/write

      VG Status             resizable

      MAX LV                0

      Cur LV                1

      Open LV               0

      Max PV                0

      Cur PV                2

      Act PV                2

      VG Size               1.91 GB

      PE Size               4.00 MB

      Total PE              490

      Alloc PE / Size       243 / 972.00 MB

      Free PE / Size       247 / 988.00 MB

      VG UUID              q620jv-Oc9a-pUlg-q6wM-TFXl-wAa7-jh40Fs

[root@Centos ~]#

3）扩展vg0卷组：

[root@Centos ~]#vgextend vg0 /dev/sdb1      扩展vg0卷组

  Writing physical volume data to disk"/dev/sdb1"

  Physical volume "/dev/sdb1"successfully created

  Volume group "vg0" successfullyextended

[root@Centos ~]#pvs           查看pv状态

  PV        VG         Fmt  Attr PSize  PFree 

  /dev/sda2 VolGroup00 lvm2 a--   19.88G      0

  /dev/sdb1 vg0        lvm2 a--  980.00M 980.00M

  /dev/sdc1 vg0        lvm2 a--  980.00M  8.00M

  /dev/sdc2 vg0        lvm2 a--  980.00M 980.00M

4）镜像卷组数据恢复：

[root@Centos ~]#lvconvert -m1 /dev/vg0/mirror /dev/sdb1 /dev/sdc1 /dev/sdc2

  vg0/mirror: Converted: 0.0%

  vg0/mirror: Converted: 43.6%

  vg0/mirror: Converted: 83.5%

  vg0/mirror: Converted: 100.0%

[root@Centos ~]#lvs-a -o +devices     查看mirror卷组状态，会看到三个pv

[root@Centos ~]#lvdisplay /dev/vg0/mirror     查看lvm mirror详细信息，Mirrored

volumes再次出现

  --- Logical volume ---

  LV Name                /dev/vg0/mirror

  VG Name                vg0

  LV UUID               vX60P8-MmjC-tNX8-w2jI-t2qt-AZnD-Rnj0IN

  LV Write Access        read/write

  LV Status              available

  # open                 0

  LV Size                972.00 MB

  Current LE             243

  Mirrored volumes       2

  Segments               1

  Allocation             inherit

  Read ahead sectors     auto

  - currently set to     256

  Block device           253:5

[root@Centos ~]#

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