5 Things to Know About PowerHA for IBM i
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"What would happen if I had to restore my last save to tape that is 24 hours old?"
"How long could we keep our business up if our IBM i system were unavailable on a weekday?"
"With business all around the world, when are we supposed to do maintenance?"
Questions like these have become more and more important in the IBM i world—not only for large companies but increasingly in smaller businesses. PowerHA for IBM i provides a hardware based availability option that is easy to use and can be automated to protect business applications from planned and unplanned outages. Here are 5 interesting facts to know about PowerHA for IBM i.
1. PowerHA for IBM i is based on IBM i clustering functionality
The IBM PowerHA SystemMirror for i solution offers an end-to-end integrated clustering solution for high availability (HA) and disaster recovery (DR). PowerHA provides data and application resiliency that is an integrated extension of the IBM i operating system and storage management architecture. It provides application high availability through both planned and unplanned outages.
2. PowerHA for IBM i is based on IASP
For PowerHA for IBM i to work, you need to separate your disk space into a system ASP and an Independent ASP (IASP). The system ASP holds the operating system, IBM license programs, and object types like user profiles, work management objects, and objects describing the hardware. The IASP holds application data and can hold application programs. Cross side mirroring provides an architecture that enables the replication of data in the IASP on one system to an IASP on another system. The system ASP does not get replicated, therefore enabling the second system to be up and running.
3. PowerHA for IBM i using Geographic Mirroring
PowerHA for IBM i provides an availability option that is independent on the storage used. Geographic Mirroring uses a TCP/IP connection between the production and the backup system to send each physical write to a storage page of the IASP on the production system over to the backup system. The same physical page is then written to the IASP on the backup system.
4. PowerHA for IBM i and Metro Mirror
When using either DS8000 or Storwize family, Metro Mirror can be used together with PowerHA for IBM i. Allthough the mirroring of storage pages is done by the storage system in this case (and not by IBM i itself) PowerHA is aware of the mirroring going on and also “talks” to the storage system. Therefore, switchover and failover processes can be initiated and controlled from an IBM i side with no manual intervention on the storage system.
5. PowerHA for IBM i and SVC Stretched Cluster
A relatively new option is to use PowerHA LUN Level Switching together with SVC Stretched Cluster. In this setup, storage high availability is provided by the SVC Stretched Cluster setup. Data is mirrored between the storage systems attached to the different nodes of the SVC. In addition, PowerHA provides server high availability. The IASP can be logically switched between the primary and the secondary system.
For more information about PowerHA for IBM i see the IBM Redbooks publication IBM
Sabine Jordan is a Consulting IT Specialist working in IBM Germany. She has worked as a Technical Specialist in the IBM i area for more than 20 years, specializing in high availability. She has worked on IBM PowerHA SystemMirror for i implementations for both SAP and non-SAP environments using geographic mirroring, IBM DS8000, and SVC remote copy services. In addition, Sabine presents and delivers workshops on IBM PowerHA SystemMirror for i and high availability and disaster recovery.