In 7.1, PowerHA Gets a Boost and a New i Name

High Availability / Disaster Recovery
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From Geographic Mirroring to LUN-level switching to FlashCopy, there's lots of new stuff to be excited about.


IBM PowerHA for i was announced as a new product in 6.1, and customer implementations have been rapidly growing. We expect that trend to continue with the major enhancements provided in the 7.1 release. For starters, it has now graduated to a longer name: IBM PowerHA SystemMirror for i. PowerHA is the family name, and SystemMirror is the specific name for the IBM i high availability (HA) product.


The PowerHA SystemMirror HA product is based on IBM i clustering technology and iASPs, thereby offering several technologies for hardware replication. A benefit of hardware replication is that the operating system or storage device is responsible for replication, resulting in fast failovers and little to no maintenance of your HA environment. In the 7.1 release, that list of hardware replication technologies has again increased.

Geographic Mirroring

Geographic Mirroring has been a popular HA solution choice for many customers, particularly small-to-medium-size clients. Prior to the 7.1 release, only short distances (roughly less than 30 miles) were supported with Geographic Mirroring, as the replication was done synchronously. In the PowerHA SystemMirror 7.1 release, asynchronous Geographic Mirroring is now supported, opening this technology up to an even greater audience.


In Geographic Mirroring, the low levels of the IBM i operating system take care of replicating each write to disk. With synchronous Geographic Mirroring, the disk write on the primary system will not complete until the write is received on the backup system. For systems in the same data center, this is an ideal solution, but in cases of extended distance between primary and backup systems or poor network bandwidth, end-user response times could be negatively affected.


With asynchronous Geographic Mirroring, the disk write on the primary no longer needs to wait for acknowledgement that the write was received on the backup. IBM i ensures that the write occurs on the backup system. This virtually eliminates the distance limitation for Geographic Mirroring.

LUN-Level Switching

Another new technology being supported by PowerHA SystemMirror in 7.1 is LUN-level switching. This technology is new for clients who use DS6000 or DS8000 storage. With LUN-level switching, you have one copy of the data in an iASP, contained on logical units, or LUNs, within the storage server. Those LUNs can be reassigned from one logical partition or system to another. This technology can be used as a standalone HA solution (with the knowledge that the single copy of data is still a possible point of failure) or in conjunction with a replication technology such as Metro Mirror or Global Mirror.


Another technology related to DS8000 storage has been enhanced. PowerHA SystemMirror will now allow space-efficient FlashCopies to be created, in addition to the traditional FlashCopy. A FlashCopy is a point-in-time copy made almost instantaneously by the system storage device. Traditional FlashCopy takes the same amount of storage as what is being flashed. Space-efficient FlashCopy does not allocate the storage until it is needed, so for copies that remain active for only a short period of time, the amount of storage required can be reduced.

Synchronized Object Types

Two new object types can be synchronized via the cluster administrative domain within PowerHA SystemMirror. Cluster administrative domain is the function within SystemMirror that facilitates synchronization of object types not allowed in an iASP.


Authorization lists (*AUTL) and printer device descriptions (*PRTDEV) can now be added as monitored resource entries. For printer device descriptions, the two most common device classes, *VRT and *LAN, are supported. The administrative domain function will also create a virtual controller to support the printer device description on nodes in the administrative domain where no existing controllers are available.

New Commands

A number of new CL commands are part of our 7.1 PowerHA SystemMirror product.  We've added commands to retrieve cluster, cluster resource group, copy description, or session information. We also added a command to print Cluster Administrative Domain monitored resource entries. These commands will help customers who want to write CL programs automate cluster management.

Node Monitoring

Another advantage of a PowerHA solution is the deep integration with the IBM i operating system. PowerHA takes advantage of the clustering technology within IBM i for failure detection and node monitoring. In PowerHA SystemMirror 7.1, administrators can go one step further and register with a Hardware Management Console  (HMC) or Integrated Virtualization Manager (IVM) to better detect node outages. In the prior release, node outages were detected via cluster distress messages. If no distress message is sent, but the status of the node cannot be detected via heart-beating, user intervention is required to determine if there is a network problem or if the node has truly failed. By registering for node failure events via the HMC or IVM, node failure can be better detected, resulting in less user invention and more automatic failover.

Versioning Support

In this second release of the product, versioning support has been added to provide for a seamless upgrade process of the production and backup nodes. Typically, customers upgrade their backup system to the next OS release, do the necessary testing, and then switch their production environment over to the upgraded backup. Then the primary system can also be easily upgraded to the new release. This has greatly reduced the upgrade time for many customers.

Standard Edition and Enterprise Edition

Along with all the enhancements in PowerHA for 7.1, some restructuring of the product was also completed. Following the trend of all Power software, PowerHA SystemMirror now has a standard edition and an enterprise edition. From a packaging perspective, the standard edition is the base product, and the enterprise edition is available as option 1.


PowerHA SystemMirror for i Standard Edition contains the command and GUI interfaces needed to configure and manage a typical HA environment within a data center or other short distance. Solutions supported by the standard edition include synchronous Geographic Mirroring, switchable IOP support, LUN-level switching, and FlashCopy. The standard edition also includes all of the infrastructure needed by an HA environment—clustering support, including heart-beating and automatic failovers, as well as the cluster administrative domain support.


PowerHA SystemMirror for i Enterprise Edition contains all standard edition support, as well as additional support for enterprise clients. Solutions supported by the Enterprise Edition are Metro Mirror and Global Mirror, utilization of DS8000 copy services, and asynchronous Geographic Mirroring for those clients desiring multiple sites without the requirement for DS8000 storage.


For additional automation, simplified storage management, and customization, there's Advanced Copy Services for PowerHA. This Lab Services offering is built on top of the PowerHA SystemMirror product and offers additional storage options, as well as other ease-of-use enhancements.

Growing Bigger and Stronger

In this, our second release of the PowerHA product on IBM i, we continue to provide major enhancements designed to increase usability for existing solutions as well as expand the HA options available to our clients. As businesses move to PowerHA SystemMirror for i, we will continue to enhance the product and continue to make it the premier offering for customers needing a reliable HA solution.