Is High Availability a Replacement for Disaster Recovery?

Is High Availability a Replacement for Disaster Recovery?

April 18

Let me start out this post by stating that the following commentary is purely my own opinion. I will interject factual information into this dialog, but the conclusions I draw are simply my own. That said, I’ve been thinking recently about the place of high availability (HA) in technology and these musings have led me to believe that although HA is considered by many today to replace the need for a solid backup, I do not believe this is true.  Here is why.

The main premise behind HA technology is based in a real-time environment with an open request or query waiting to be filled. Let’s say that I’m trying to send an important email or perhaps trying to access data stored on a web server.  My open request is sent from my local device out across the network to the appropriate server device. If for some reason the server is not available, a second server is located and my request is filled by this alternate system. This is the purpose of HA, that is, it’s intended to make available the requested information regardless of the active state of the underlying systems.

It seems reasonable at this point to assume that with a limited budget and faced with the decision to spend those budgetary resources on either HA technology or disaster recovery (DR) technology, in the short-term it may be more important to make information available rather than to consider the long-term of maintaining data integrity. I think (and again, this is my opinion) that it’s just this simple decision to focus on HA that causes us, as IT professionals, to lose sight of the importance of a solid backup.

HA technologies usually involve some kind of load-balancing and/or mirroring that allows these duplicate systems to constantly share and update information so that if one system is down the other system is available to step up and provide the information.  But what if both systems are down? Or, as seems to be more often the case, what if the data on both systems has become corrupted? HA does not address the integrity of the underlying data, it simply addresses the process in accessing that data.

For this reason I don’t believe HA can ever be a substitute for a good disaster recovery solution. In an ideal world, both are complimentary technologies that ensure both access to and permanence of your business data. However, in our often not-so-ideal world it’s easy to make the mistake and believe that HA will solve all of our data needs. It doesn’t, and please don’t think that it will.  Yes, it solves many immediate and pressing needs. Yes, it is definitely valuable and necessary for modern digital business transactions. Just as disaster recovery is critical to business today. They both have their place, and both are equally essential to a solid business continuity solution.

Thanks for listening.  Cheers!

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