High Availability Architecture: A Real-Life Blueprint to Use and Share

What does it take to achieve high availability? The short answer is “a lot.” Building highly available infrastructure requires investing in multiple infrastructure components, tools, and processes.

For the longer answer to building a high-availability architecture, keep reading.

What is high availability?

Simply put, high availability means that everything hosted on your infrastructure is resilient against disruptions.
Keeping computer systems highly available means taking several deliberate steps when designing your infrastructure, setting up management tools and implementing management processes.

A high availability architecture can be broken into the following three main parts.

High availability architecture

High availability architecture starts with an infrastructure that is resistant to disruption.

The specific components that you use to build a high availability architecture  will vary depending on the type of infrastructure you have, of course. But in general, components such as the following are required:

• Redundant systems:  A backup system holds a copy of your server, applications and up-to-date copy of your data.  It stands ready to assume the role of the production server.  Ideally, your infrastructure would include multiple systems and copies of your data, with at least one system being geographically remote to protect from regional outage or natural disaster.
• Redundant disk arrays: These arrays help ensure that data (and the apps that depend on it) remain available if one disk fails.
• Redundant networking:  Most modern infrastructures depend heavily on the network and its access to the internet. If your network goes down, your infrastructure becomes unavailable. That is why you want to build redundancy into your network by having multiple switches and routes available.  You also should consider implementing a redundant internet access point in case your primary access point is disrupted.

Components of a high availability solution

You also want to set up the right tools to help you achieve high availability. Here again, the exact tools you use will vary depending on your needs, but they might include the following components:

• Replication technology that maintains a redundant copy of your data, applications and server settings on a secondary system. Your organization’s requirements for the time required to resume operations (RTO) and protection from lost data (RPO) will determine how close to real time the solution must maintain the replica.
• Uptime monitoring tools to keep tabs on your applications, data, and infrastructure and react quickly when something goes down.
• Automated failover capabilities, which can switch over to a secondary system automatically when one a system fails.
• Performance monitoring tools, which can help you identify performance issues that might be the first signs of a problem. You can then address the issue before you have a failure of a server or disk drive.

High availability processes

Even if you implement the proper infrastructure elements, no high availability strategy is complete without the right processes in place to respond to issues when they occur. Those processes might include:

• Incident response. Who is responsible for making the decision to failover to the backup server? How will they be notified…phone, email, text? What will they do if they need to ask others for help when responding to an incident? How will they notify others on the team and throughout the company? What if the incident occurs during off-hours when IT staff are not near their desks? All of these questions should be answered by your incident response process.
• Retrospective analysis of your incident response processes.  This step will help you to track the effectiveness of incident response over time and find ways to do even better.
• Testing your process.  Creating a document that lists all the steps in the process is an important part of your overall HA implementation, but the incident response and failover process needs to be tested on a regular basis to be sure it is effective and efficient as well as to insure those involved in responding to an incident are trained and comfortable executing their roles.

Conclusion

Completely eliminating downtime may not be possible for some organizations.  Even the best designed HA infrastructures can experience points of failure; regional outages or natural disasters cannot be prevented; and downtime may be part of maintenance operations.

However, based on your budget and your company’s tolerance for downtime and data loss you can design an HA infrastructure that will allow you to respond to events quickly, minimize the number of disruptions, and nearly eliminate the resulting periods of downtime.

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