就一般生产系统而已，操作系统层面都要进行备份，而最常见的操作系统备份方式之一就是做镜像（mirror），而实践过程中，往往是把rootvg这个卷组做镜像操作。查看rootvg是否已经进行镜像方法：

          1） lsvg –o

          2）lsvg –l rootvg

# lsvg -l rootvg
rootvg:
LV NAME             TYPE       LPs     PPs     PVs  LV STATE      MOUNT POINT
hd5                      boot       1       2       2    closed/syncd  N/A
hd6                      paging     16      32      2    open/syncd    N/A
hd8                      jfs2log    1       2       2    open/syncd    N/A
hd4                      jfs2       12      24      2    open/syncd    /
hd2                     jfs2       10      20      2    open/syncd    /usr
hd9var                jfs2       6       12      2    open/syncd    /var
hd3                     jfs2       6       12      2    open/syncd    /tmp
hd1                     jfs2       400     800     2    open/syncd    /home
hd10opt            jfs2       1       2       2    open/syncd    /opt
hd11admin       jfs2       1       2       2    open/syncd    /admin
fwdump             jfs2       2       4       2    open/syncd    /var/adm/ras/platform
lg_dumplv         sysdump    3       3       1    open/syncd    N/A
livedump           jfs2       1       2       2    open/syncd    /var/adm/ras/livedump

如上图所示，LPs与PPs的比例是1:2证明rootvg已经做了镜像，即做了一份rootvg的副本，便于操作系统层面出现问题时，及时还原。如果LPs与PPs的比例是1:1这表名是没有做rootvg镜像的。而且PVs都是2，证明是两块物理磁盘做的镜像操作。

1 查看rootvg大小

# lsvg rootvg
VOLUME GROUP:       rootvg                   VG IDENTIFIER:  00f9150300004c0000000145634ba48d
VG STATE:           active                              PP SIZE:        1024 megabyte(s)
VG PERMISSION:      read/write               TOTAL PPs:      1116 (1142784 megabytes)
MAX LVs:            256                                   FREE PPs:       199 (203776 megabytes)
LVs:                13                                           USED PPs:       917 (939008 megabytes)
OPEN LVs:           12                                     QUORUM:         1 (Disabled)
TOTAL PVs:          2                                      VG DESCRIPTORS: 3
STALE PVs:          0                                       STALE PPs:      0
ACTIVE PVs:         2                                      AUTO ON:        yes
MAX PPs per VG:     32512                                    
MAX PPs per PV:     1016                           MAX PVs:        32
LTG size (Dynamic): 1024 kilobyte(s)      AUTO SYNC:      no
HOT SPARE:          no                                  BB POLICY:      relocatable
PV RESTRICTION:     none                         INFINITE RETRY: no

     rootvg大小为1142784MB，但实际可用空间只是这个数据的一般，即：571392MB，因为你做了一份镜像操作。

2 查看rootvg有哪几个磁盘组成

# lspv
hdisk0          00f91503634b9132                    rootvg          active     
hdisk1          00f91503639b9dbf                    rootvg          active     
hdisk2          00f91503747466fd                    datavg          active     
hdisk3          00f915037474679d                    datavg          active     
hdisk4          00f91503ac90ba5d                    datavg          active     
hdisk5          00f91503bbd0aea1                    datavg          active     
hdisk6          none                                None                       

可见，rootvg是由hisk0和hdisk1两个磁盘组成。

3 给rootvg做镜像

　　使用命令为mirrorvg。mirrorvg命令将给已存在某个卷组上的逻辑卷最镜像操作。与此相同功能的命令为mklvcopy。

语法：

Purpose

       Mirrors all the logical volumes that exist on a given volume group.

Syntax

       mirrorvg [ -S | -s ] [ -Q ] [ -c copies] [ -m ] [ -p copyn=mirrorpool ] volumegroup [ physicalvolume ... ]

-c copies
            Specifies the minimum number of copies that each logical volume must have after the mirrorvg command has finished
            executing. It may be possible, through the independent use of mklvcopy, that some logical volumes may have more than
            the minimum number specified after the mirrorvg command has executed. Minimum value is 2 and 3 is the maximum value. A
            value of 1 is ignored.

-m exact map
            Allows mirroring of logical volumes in the exact physical partition order that the original copy is ordered. This
            option requires you to specify a PhysicalVolume(s) where the exact map copy should be placed. If the space is
            insufficient for an exact mapping, then the command will fail. You should add new drives or pick a different set of
            drives that will satisfy an exact logical volume mapping of the entire volume group. The designated disks must be
            equal to or exceed the size of the drives which are to be exactly mirrored, regardless of if the entire disk is used.
            Also, if any logical volume to be mirrored is already mirrored, this command will fail.

-S Background Sync
           Returns the mirrorvg command immediately and starts a background syncvg of the volume group. With this option, it is
           not obvious when the mirrors have completely finished their synchronization. However, as portions of the mirrors
           become synchronized, they are immediately used by the operating system in mirror usage.

-s Disable Sync
           Returns the mirrorvg command immediately without performing any type of mirror synchronization. If this option is
           used, the mirror may exist for a logical volume but is not used by the operating system until it has been synchronized
           with the syncvg command.

假如我们将rootvg的镜像到hdisk1磁盘上，命令如下：

          mirrorvg –S -c 2 rootvg hsisk0 hdisk1

操作完成后，还要执行以下两个命令：

       (1) bosboot  The bosboot command is required to customize the bootrec of the newly mirrored drive.

        The bosboot command creates a boot file (boot image) from a RAM (Random Access Memory) disk file system and a kernel. This boot image is transferred to a particular media that the ROS boot code recognizes. When the machine is powered on or rebooted, the ROS boot code loads the boot image from the media into memory. ROS then transfers control to the loaded images kernel.

       (2) bootlist  The bootlist command needs to be performed to instruct the system which disk and order you prefer the mirrored boot process to start.

操作如下：

        (1)执行bosboot命令

            bosboot -ad /dev/hdisk0
            bosboot -ad /dev/hdisk1

        (2) 执行bootlist命令： 设置系统的引导顺序

            bootlist -m normal hdisk0 hdisk1 cd0

        (3) 查看引导熟悉结果

            bootlist -o -m normal

4 替换在镜像卷组里的坏盘

  当我们发现，在镜像卷组中的一块盘有问题时，需要使用一块新磁盘来顶替这块有问题的磁盘。操作方法如下：

    (1) 取消hdisk7盘上的镜像

           unmirrorvg workvg hdisk7

    (2) 从卷组中删除hdisk7磁盘
            reducevg workvg hdisk7

    (3) 系统层面删除hdisk7
            rmdev -l hdisk7 –d

    (4) 识别新盘

           cfgmgr –v

    (5) 重命名磁盘

         需要将新识别的磁盘为hdisk7，关于hdiskX的名字是存在操作系统底层的ODM数据库里的，ODM数据库包含了所有PV、VG和LV的配置信息，这些信息与VGDA中的信息互为镜象，ODM数据也和LV控制块中的信息相互镜象。因此需要将原先的hdisk盘从系统层面删除，然后再去重新扫盘，让系统识别出新扫描到的磁盘名称与之前的名称是一致的。

        查看物理磁盘命令：lspv

        给磁盘一个ID编号：chdev –l hdisk7 –a pv=yes

    (6) 将磁盘添加到卷组中

          extendvg workvg hdisk7

    (7) 查看workvg镜像情况
          mirrorvg workvg

5 取消卷组镜像

    命令：unmirrorvg

    Purpose

          Removes the mirrors that exist on volume groups or specified disks. This command only applies to AIX 4.2.1 or later.

    Syntax

          unmirrorvg [ -c Copies ] VolumeGroup [ PhysicalVolume .. . ]

例如：取消workvg卷组镜像，留有一份副本

        命令：unmirrorvg -c 1 workvg

6 备注

　　When unmirrorvg workvg hdisk7 is run, hdisk7 will be the remaining drive in the volume group. This drive is not actually removed from the volume group. You must run the migratepv command to move the data from the disk that is to be removed from the system to disk hdisk7.

migratepv命令：

Purpose

       Moves allocated physical partitions from one physical volume to one or more other physical volumes.

Syntax

       migratepv [ -i ] [ -l LogicalVolume ] SourcePhysicalVolume DestinationPhysicalVolume...

Description

       The migratepv command moves allocated physical partitions and the data they contain from the SourcePhysicalVolume to one or more other physical volumes. To limit the transfer to specific physical volumes, use the names of one or more physical volumes in the DestinationPhysicalVolume parameter; otherwise, all the physical volumes in the volume group are available for the transfer. All physical volumes must be within the same volume group. The specified source physical volume cannot be included in the list of DestinationPhysicalVolume parameters.