Hardware & Software Replication for IBM i

Replication is a critical component of most organisations data protection and recovery strategy. In this article, we will answer the most common questions people have when it comes to hardware and software replication and detail the benefits and limitations of each approach.  

Flexibility  

A key feature of software based replication is the flexibility that it offers. Software based replication is highly configurable and allows you to choose the data you would like to replicate, whereas hardware based replication replicates all data across to your backup system and does not have the capability to define what data you would like to replicate.

Although software based replication is a more flexible solution, it requires more management overhead when compared to hardware based replication. If you implement a software based replication you would need a process of identifying and adding new libraries into replication as changes are made to your applications over time. This would not be required with hardware based replication as all new data would be replicated automatically. 

Hardware and software replication IBM i

Requirements and performance

One important thing to consider is whether you have external storage in place. Hardware based replication requires external storage as a pre-requisite as it is reliant on replication of a disk storage subsystem. If you currently have external storage adopting a hardware based solution would be very cost effective as the software is already within IBM Storwize storage.  

Hardware based replication requires no CPU or memory resources from the IBM POWER system. In contrast, software based replication uses journaling and will use additional CPU and memory of the IBM POWER system. Some of our existing customers have decided to transition from software to hardware based replication simply due to the impact software based replication has on the performance of their IBM POWER system. 

Software based replication requires both the live and HA system to be running. This gives you the ability to run a second copy of the data for reporting and analysis. Another benefit of having both systems running is that the recovery time for a HA switch is much quicker than hardware based replication. As with hardware based replication you will need to attach the backup IBM POWER server to the backup storage so recovery time can be delayed as you would need to perform a IPL.

If you are concerned about performing a switch in the event of a disaster or have very high resiliency requirements you could implement a hardware based replication using a IBM Hyperswap configuration, this can ensure that no downtime occurs due to a loss of one storage controller and is a highly resilient option if no data loss is the primary objective.  

A software based HA solution only replicates application data. As a result, your IBM i operating systems sit on your live and HA servers. When it comes to performing an operating system upgrade you would have to upgrade both the live and HA operating systems. Hardware based occurs at the storage level so all changes including operating system upgrades would automatically be replicated across to your HA server.  

Hardware based replication allows you to rationalise your replication strategy to a single solution across platforms, whereas software based replication could mean you have MIMIX for IBM i, POWERHA for AIX and Veeam for an Intel environment for example. Consequently, you would need knowledge of multiple HA products resulting in additional complexity.

Could you combine hardware and software based replication?

You don’t need to choose one or another. A hybrid hardware and software based solution can provide maximum availability and recovery options. For example a local Hyperswap configuration with journal-based software replication to a remote site over IP. Hyperswap combined with software based replication would ultimately give you the best of both worlds, a highly resilient solution that is ideal for organisations looking for the most resilient solution available in the IBM marketplace.

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Chilli IT help organisations bridge the IBM skills  gap by providing technical support, professional services and hardware and software upgrades to organisations across the world.

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