PowerPath: How to configure an AIX host booting from SRDF devices?[1]


   Article Number:     531137                                   Article Version: 3     Article Type:    How To 




PowerPath for AIX






      Environment :     
      OS : AIX (any release) with boot from SAN configured.     
      DELL EMC SW : PowerPath 6.1 and above     
      DELL EMC SW : classical R1-R2 SRDF     
      DELL EMC SW : SRDF Metro     
      DELL EMC HW : VMAX family     
      DELL EMC doesn't officially support boot from SAN with PowerPath on SRDF R1/R2 devices on AIX, as opposed to Solaris or Linux where a "powercf -Z" can do the trick. Without precautions, the following symptom will be observed :     
      Initially, the host boots from a R1 device. lspv is then showing the following :   


      # lspv | grep rootvg         
          hdiskpower0     000b8d313342518d                    rootvg          active
      Upon a reboot on the R2 device, lspv |grep rootvg now returns :      
      # lspv | grep rootvg         
          hdiskpower0     000b8d313342518d                    rootvg          active               
          hdiskpower41    000b8d313342518d                    rootvg          active
      the duplicate PVID will not be an issue to boot, but will be an issue to varyon other VG. To avoid this kind of issue, PowerPath needs to be completely uninstalled and re-installed. "PowerPath updates" instead of "PowerPath uninstall / PowerPath install" sequence will cause the above issue.     
      If PowerPath is completely uninstalled and reinstalled, an "lspv | grep rootvg" will result in the following sequence :     
      boot from R1 device :     
      # lspv | grep rootvg         
          hdiskpower0     000b8d313342518d                    rootvg          active
      Boot from R2 device :     
      # lspv | grep rootvg         
          hdiskpower41    000b8d313342518d                    rootvg          active
      In an SRDF metro configuration, the above issue doesn't exist since, thanks to the identity spoofing mechanism. the host (and PowerPath) is not aware of the difference between the R1 and the R2 devices ... and everything works as it was a classical and regular boot from SAN.