HACMP (PowerHA) FAQs

HACMP (PowerHA) FAQs 

What is HACMP and its usage?

• HACMP is High Availability and Cluster Multi Processing. 
• Elimination of  Planned and Unplanned system and application downtime. And provided business continuity for users/corporates irrespective of system/network/appn failure. 
• In HACMP, the term HA (High Available) and CMP (Cluster Multi Processing) refers to the HACMP features which enable one to build a cluster of multiple nodes which work together to provide improved application performance. 
• To avoid SPOF(Single Point of Failure)  for the following objects.                                     Node, Powersource, Network Adapter, Network, Disk adapter, Disk, Application, VIO and entire Datacenter. 

What are the policies of Cluster?

• Rotating
• Cascading
• Custom      

   Among these Rotating and Cascading are classic i.e., pre-HACMP 5.1 types. The new custom type of resource group has been introduced in HACMP 5.1.

What are the 2 important components of HACMP?

• Topology (Physical) components.
• Resource (Logical) components.

What are the Topology components?

    There are 4 topology  or physical components
          i) Nodes       - System P series standalone servers.
         ii) Networks -  IP networks and non-IP networks.
        iii) Communication Devices    - Token ring or Ethernet adapters
        iv) Communication interfaces - network, RS-232 and disk heartbeat.

What are the Resource components?

       There are 4 resource or logical components
          i) Application Server - It involves start/stop scripts of the application.
         ii) Service IP  - End users generally use given an IP address to connect to the application. It should be remain high available.
        iii) Volume Group
        iv) File system

    All the Resources are together form the group called Resource Group. Whenever the node failover  and fallback occurs this RG move from one node to other and vice-versa.

Explain about the Custom RG ?

 There are 3 options in this RG 

        i) Startup policy 

              This policy tells which node the RG should activate. 
            a) Online on the home node only
            b) Online on first available node.
            c) Online on all available nodes. 
            d) The RG will only be brought online if the node has no other RG online,     can find using 
                 #lssrc -ls clstrmgrES
  
       ii) Fallover policy 

           When a failure happens, this determines the fallover target node. 
             a) To next priority node.
             b) Using Dynamic Node Priority
             c) Bring Offline 

          The RG will be brought offline in the event of an error occur. 

       iii) Fallback policy 

                This tells whether or not the RG will fallback. 
               a) Fallback to the next priority node (home node)
               b) Never fallback