10.4 Similarities and Differences
All three products have the basic structure in common. They all use the same concepts and structures. So, a cluster or a network, in the HACMP context, is the same, no matter what product is being used. There is always a Cluster Manager controlling the node, keeping track of the cluster’s status, and triggering events. The differences are in the technologies being used underneath, or in some special cases, the features available.
The technique of keeping track of the status of a cluster by sending and receiving heartbeat messages is the major difference between HACMP Classic and HACMP/ES Version 4.3. HACMP Classic uses the network modules (NIMs) for this purpose. These communicate their results straight through to the HACMP Cluster Manager. HACMP/ES, uses the facilities of RSCT, namely Topology Services, Group Services, and Event Management, for its heartbeating. Since Version 4.3, the restriction to run HACMP/ES on RS/6000 SP systems only has been withdrawn. However, if you run it on an RS/6000 SP, you need to have PSSP Version 3.1 installed. As the HPS Switch is no longer supported with PSSP Version 3.1, you need to upgrade to the SP Switch, in case you haven’t already, or you will have a switchless system.
You can still run HACMP Classic on RS/6000 SP Nodes, just as on standalone RISC System/6000s. It has no references into the PSSP code whatsoever.
HANFS for AIX Version 4.3 is basically, a modified HACMP Classic, enhanced with the capability of the takeover node to recover current NFS activity, should the primary NFS server fail. By means of AIX extensions to standard NFS functionality, HANFS for AIX is enabled to handle duplicate requests correctly or restore the lock state in case of an NFS server failover or reintegration. Remember though, that HANFS is somewhat restricted, in that it only supports
10.5 Decision Criteria
Your decision of what type of high availability software you are going to use can be based on various criteria. Existing hardware is one of them.
If you still use the “old” HPS Switch and don’t want to lose its functionality, you are bound to the use of PSSP 2.4 or lower. Therefore HACMP Classic or HACMP/ES up to Version 4.2.2 only is the choice for you.
