Edit: Some links no longer work.
Originally posted October 30, 2012 on AIXchange
In its Oct. 3 announcements, IBM noted that the new PowerHA SystemMirror 7.1 Enterprise edition will go GA on Nov. 9. Since I recently took some IBM training on this product, I’d like to tell you more about it.
First, understand that PowerHA is designed to provide mission-critical application availability through planned and unplanned outage events. True to its name, the enterprise edition is aimed toward multisite configurations, while PowerHA SystemMirror standard edition offers access to the normal capabilities of a local PowerHA cluster.
There are two options for multisite clusters: stretched and linked. A stretched cluster utilizes a single repository disk and occupies a single communications network that can extend for shorter distances. For a real-world example, think of a storage subsystem using GLVM that covers a college campus. The stretched cluster communicates with the nodes in the cluster using multicast.
A linked cluster is two sites in two different networks that are linked together. Distance is not an issue — the sites can be cross campus or cross country. A linked cluster utilizes two separate repository disks instead of the shared repository disk that’s used in a stretched cluster. While cluster-wide AIX commands can be used with both stretched and linked clusters, linked clusters use unicast communications.
HyperSwap provides for a multisite PowerHA cluster with continuous storage availability. With HyperSwap, applications keep running in the event of a storage outage, and the storage is kept in sync via Metro Mirror. Storage maintenance and storage migration can be performed without downtime. However, due to the specialized code involved, non-IBM storage products are not supported. IBM DS8000 storage systems must be on both sides of the HyperSwap solution.
In the training session I attended, IBM emphasized the tighter integration that now exists between PowerHA and AIX. This is in large part due to Cluster Aware AIX. PowerHA 6.1 used traditional communication-based heartbeats, along with “user space” event processing and rsct topology management. The PowerHA 7.1 architecture features multicast communications, SAN communications, a repository disk heartbeat and kernel-based event processing. It becomes harder to have a cluster become “split brained” or partitioned due to the changes to the topology and heartbeating.
Other notes about the training session:
* IBM has made changes to the Systems Director plugin to simplify cluster creation. This allows you to use a GUI to create your cluster and access a multisite install wizard.
* Be sure to get the latest service packs for both AIX and PowerHA. Having the latest fixes always helps; it’s vital with PowerHA.
IBM is continuously investing in and improving PowerHA as well as planning future capabilities. As was noted in the training session, the product still allows you to use dynamic logical partitioning to grow your LPARs when needed. You can set up an LPAR with 4 CPUs on your primary node and 1 CPU on your failover node. When it’s time to swap roles, that failover LPAR is able to take on 4 CPUs dynamically. This can save you on software license fees for your backup nodes.
Having worked with it for awhile now, I’m impressed with PowerHA SystemMirror 7.1 Standard edition. I’m still amazed at how easy it is to set up. Have you worked with this version of the product yet? What have your experiences been so far? Are you looking forward to the new capabilities with Enterprise edition?