This document specifies the supported method for mirroring the rootvg volume group to provide high availability access of the AIX operating system. There are four steps required in mirroring rootvg:

1. Mirror rootvg using mirrorvg or mklvcopy.
2. Make the new mirrored disk bootable by running bosboot.
3. Add the new mirrored disk to the bootlist.
4. Reboot the system to disable quorum. (5300-06 and below only)

This function is not supported on /usr client, diskless client, or dataless client systems.

Why mirror the rootvg volume group?

Mirroring the rootvg volume group is important because:

• Maintaining an active mirrored copy of the rootvg volume on another disk ensures continuous operation of the AIX operating system in the event that a disk that is part of the operating system experiences failure.
• Such maintenance provides the ability to boot more than one disk of the rootvg in the event that another boot disk has failed. In some cases, the ability to boot from alternate disks may require some user intervention.

Procedure

1. To mirror the entire contents of rootvg volume group, use the mirrorvg command. Assuming rootvg is on hdisk0 and that hdisk1 is the physical volume to mirror to, use the following syntax:

        mirrorvg rootvg hdisk1
   

   You will receive a message similar to:

   AIX 5300-06 and below:

        0516-1124 mirrorvg: Quorum requirement turned off, reboot system for this 
            to take effect for rootvg.
        0516-1126 mirrorvg: rootvg successfully mirrored, user should perform
            bosboot of system to initialize boot records.  Then, user must modify
            bootlist to include: hdisk1 hdisk0.
   

   AIX 5300-07 and above:

   0516-1804 chvg: The quorum change takes effect immediately.
   0516-1126 mirrorvg: rootvg successfully mirrored, user should perform
           bosboot of system to initialize boot records.  Then, user must modify
           bootlist to include:  hdisk1 hdisk0.
   

   If user has user-created logical volumes in rootvg and does not want to mirror those, the mklvcopy command may be used instead to mirror only the standared rootvg logical volumes, such as hd1, hd2, hd3, hd4, hd5, hd6, hd8, hd9var and hd10opt at AIX V5. Syntax of mklvcopy is as follows:

        mklvcopy LVname 2 hdisk1
   

   If user has other paging devices, in addition to hd6, it is recommended to mirror those as well.

   If hd5 consists of more than one logical partition, then, after mirroring hd5, the user must verify that the mirrored copy of hd5 resides on contiguous physical partitions. This can be verified with the following command:

        lslv -m hd5
   

   If the mirrored hd5 partitions are not contiguous, the user must delete the mirror copy of hd5 (on hdisk1) and rerun the mklvcopy command for hd5, using the -m option. The user should consult documentation on the usage of the -m option for the mklvcopy command.

   If rootvg is mirrored using mklvcopy command, the user must manually synchronize the partitions and disable quorum.

        syncvg -v rootvg      =>will synchronize all stale partitions
        chvg -Qn rootvg       =>will disable quorum
   

2. To initialize the boot record on the newly mirrored disk, run the following:

        bosboot -ad /dev/hdisk1
   

3. To add the newly mirrored disk to the bootlist, run the following:

        bootlist -m normal hdisk0 hdisk1
   

   NOTE: If the system is booted via network, you may need to include the ent# in the bootlist.

   WARNING: Even though this command identifies the list of possible boot disks, it does not guarantee that the system will boot from the alternate disk in all cases involving failures of the first disk. In such situations, it may be necessary for the user to boot from the installation or maintenance media: select Maintenance, reissue the bootlist command leaving out the failing disk, and then reboot. On some models, firmware provides a utility for selecting the boot device at boot time. This may also be used to force the system to boot from the alternate disk.

4. If necessary, reboot system to disable quorum, by running either one of the following commands:

        reboot
   

   or

        shutdown -Fr
   
   
   
   source: http://www-01.ibm.com/support/docview.wss?uid=isg3T1000358