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。
# 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。
# 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。
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
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
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
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.
原文：http://www.cnblogs.com/oracle-dba/p/3762237.html