Do you need HA

One question which came up many times I was involved in the sales process for a HA product was how quickly do you need to switch. Many articles and marketing messages that surround the HA space revolve around this question because its seen as the ultimate test of a HA product.

Yet once the installation process is underway you find many of the customers never actually getting round to doing a switch of any kind. This has to raise the question “Do they really need HA”? The benefit of a HA solution is the removal of planned downtime as well as coverage for unplanned downtime. Planned downtime represents approximately 95% of the downtime associated with the IBM system i5 (as published in many articles about IBM System i5 availability) which is why most customers see it as a reason to implement a HA solution. If you have time to carry out your planned activity without switching to the target system you really don’t need a HA solution.

I have been to many companies to do audits on their HA installation only to find that they have no idea on how they would switch in the event of a system failure, some even commenting that they have no faith in the replication product and would probably just do a full restore and start again. This is obviously not a good investment for the company, having spent a lot of money implementing the solution plus the ongoing cost of maintaining it you should be using it regularly and ensuring it works when you need it.

Another problem which shows up regularly is where a company implemented the solution many years ago and has never bothered to maintain either the product or the replication environment. They have a solution which is ineffective and outdated and while the system stays up is just ignored. Problems only show up when the system fails and everyone starts to point fingers at who is at fault. They may believe they have a product which maintains itself and have invested little or no time in ensuring they have the skills to ensure the environment is maintained correctly.

If you are not switching regularly, have time to carry out regular maintenance or run your batch without interrupting user access is usually a sign that you do not need a HA solution.

HA solutions by their nature are complex to manage no matter how simple the ISV’s make the install and daily management of their products. You have to constantly evaluate what is being replicated and why, introducing changes to the application or environment may have a devastating effect on the ability of the remote system to take up the process when needed.

If you are only interested in protecting your data objects you have plenty of alternatives which offer the required level of protection without going for a full blown HA implementation. If you are not switching every day or even week you may be running something which is overkill for your needs.

Make sure you know the solution you have is what you need, if you don’t spend time managing it or testing its capabilities you are probably running the wrong solution. DR has lost a lot of its appeal because of the introduction of the HA products and their capabilities but if its all you need you are wasting money with a HA solution and should consider the alternatives.


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