Mirroring the rootvg Volume Group for AIX 4.1/4.2

     The disks that constitute the boot drives for AIX, must be disks that
     are supported to boot on RS/6000 platforms. A machine and disk
     configuration may be queried to determine if that combination of
     machine and disk supports booting from disk:

                     bootinfo -B hdiskX

     If the command returns a "1" then it will be bootable by AIX. Any
     other value indicates that this disk is not a candidate for rootvg
     mirroring.

Procedure:

The following steps assume the user has rootvg contained on hdisk0 and is
attempting to mirror the rootvg to a new disk hdisk1.

  1. Extend rootvg to hdisk1:

             extendvg rootvg hdisk1

     If the user encounters the error message:

      0516-050 Not enough descriptor space left in this volume group.
      Either try adding a smaller PV or use another volume group.

     Then the user may not add hdisk1 to rootvg for mirroring. The user may
     attempt to mirror rootvg's logical volumes to another disk that
     already exists in rootvg and meets the criteria and restrictions
     listed in the "restrictions" section above. The user may also attempt
     to add a smaller disk to the rootvg. If neither option is possible,
     then mirroring rootvg cannot be performed on this system.

  2. Disable QUORUM, by running the following:

             chvg -Qn rootvg

  3. Mirror the logical volumes that make up the AIX operating system:

             mklvcopy hd1 2 hdisk1            #  /home file system
             mklvcopy hd2 2 hdisk1            #  /usr file system
             mklvcopy hd3 2 hdisk1            #  /tmp file system
             mklvcopy hd4 2 hdisk1            #  / (root) file system
             mklvcopy hd5 2 hdisk1            #  blv, boot logical volume

             mklvcopy hd6 2 hdisk1            #  paging space
             (if the user has other paging devices, rootvg and non-rootvg, they

             must also mirror those logical volumes in addition to hd6)
             mklvcopy hd8 2 hdisk1            #  file system log
             mklvcopy hd9var 2 hdisk1         #  /var file system

     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 command:

                     lslv -m hd5

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

  4. Synchronize the newly created mirrors:

             syncvg -v rootvg

  5. Bosboot to initialize all boot records and devices:

             bosboot -a

  6. Initialize the boot list:

             bootlist -m normal hdisk0 hdisk1

     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/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.

  7. Shutdown and reboot the system:

             shutdown -Fr

     This is so that the "Quorum OFF" function takes effect.

• Replace a broken disk

     1. To replace a bad disk drive in a mirrored volume group, enter
  
  unmirrorvg workvg hdisk7
  reducevg workvg hdisk7
  rmdev -l hdisk7 -d
  replace the disk drive, let the drive be renamed hdisk7
  extendvg workvg hdisk7
  mirrorvg workvg
  
  Note: By default in this example, mirrorvg will try to create 2 copies for 
  logical volumes in workvg. It will try to create the new mirrors onto the replaced 
  disk drive. However, if the original system had been triply mirrored, there may be 
  no new mirrors created onto hdisk7, as other copies may already exist for the 
  logical volumes.
  
     2. To sync the newly created mirrors in the background, enter:
  
  mirrorvg -S -c 3 workvg
  
     3. To create an exact mapped volume group, enter:
  
  mirrorvg -m datavg hdisk2 hdisk3
  
  

  ---

  Last Update November 11, 1998 Eva Hocks

source: http://www.sdsc.edu/~hocks/aix.mirror.html