High Availability 101: Functions and Importance for Businesses

 It is beneficial for infrastructures or systems that put a high value on optimum operational performance.


Managing infrastructures is not easy. There is no denying that. Certain aspects need to be considered, especially when you have to think about matters like failures and downtimes. This is why there is a need to understand the concept and value of high availability (HA).

Understanding High Availability

High availability occurs when your system has no operational problems, and if it performs smoothly and without glitches for a long period of time. A system that performs 100% or a system that is 100% operational.

High availability is important if you want all parts of your infrastructure to be completely operational. If it fails or experiences errors even on an occasional basis, it will not be able to operate normally. A system of infrastructure, of course, is made up of several components that need to, not only complement each other, but also be available as the others.

Basically, availability pertains to the length of time that a particular service is available and is able to respond to user requests. The amount of time a system returns a request is what determines its level of “availability”. The term five 9s, or 99.999%, is used to describe a system that carries the desired level of availability – high availability. It means that total annual downtime is only at 5.39 minutes. Additionally, a high availability system is expected to have only a total of 3.65 days (or 1%) of downtime in a given year.

Some factors that affect availability are system failure and unscheduled and scheduled maintenance times.

Functions and Uses of High Availability

Infrastructures are essential for keeping businesses function properly. If it has the capacity to prevent outages and failures; or if an infrastructure is able to operate its most important functions without interruptions or problems, an enterprise can achieve continuity.

If a business aims to achieve a competitive advantage, a high level of availability is essential. Once this is achieved, problems related to data loss and downtimes, among others, will trickle down. Moreover, with high availability, it will be easy to avoid customer service-related problems and the negative publicity that stems from these. Also, employees will become more productive.

Every time there is downtime, an enterprise is poised to lose productivity, which, of course, affects its revenue-making capabilities. If the downtime is lower than 30 seconds, the impact can be quite small. But, if this length of time increases, the effect will also grow. Ultimately, it will create a negative impact on the enterprise. With a good high availability solution, this can be avoided.

So, simply put, high availability or high availability solutions are needed to provide infrastructures a response system for failures. It may sound quite basic, but making it work will require a certain level of knowledge and expertise, as well as the right software.

Characteristics of High Availability

There are certain characteristics needed for one to find a solution with a high level of availability. These are the following:

  1. A reliable hardware and software. One cannot do without the other. This includes applications, databases and web servers.
  1. The capacity to recover (or the period of time it takes to recover) is also a crucial characteristic. Remember that the ability or capacity to recover is dependent on a specific length of time. Recoverability rate should meet the required standard. In other words, there should be a concrete plan of action or recovery process for every possible problem a system can encounter.
  1. Fast and efficient detection of failures. The main goal is to recover from these failures in the fastest time possible. For example, if sensitive data is lost because of a critical failure, one cannot spend hours or days trying to determine what caused it. Of course, you cannot find a way to recover the data immediately because you still have not identified the problem that caused it. But with a reliable software that is able to detect errors in the fastest and most efficient way possible, this failure will be resolved in just minutes.
  1. High availability is equivalent to minimal downtime. This is essential especially when you need to do some maintenance on the system or when you need to perform specific activities that will require you to continually access data. Every task carried out should be transparent.

In summary, the most important characteristics of a high availability solution are built-in preventive solutions, transparency, high level of recoverability, fast failure detection, automated recovery capacity, reliable data protection and excellent management/operational practices.

Server Redundancy and Its Importance to High Availability

Backup and server redundancy are important to achieve high availability.

Basically, server redundancy pertains to the ability of an infrastructure to deploy additional servers on runtime for purposes such as load balancing and backup. What is normally done is that a replica for a server is created. It will carry the same storage, computing power, operational and applications details as the other server. Although it is turned on via Internet connectivity, a redundant server is offline, meaning, it is not a live server.

The purpose of a redundant server is to take the place of the primary server when failure or downtime occurs, or when traffic load is too much.

Factors That Lead to Downtime

To create good high availability solutions, it is important to identify and understand what causes failures and downtimes. Whether planned or unplanned, downtimes can significantly affect business operations.

Here are some major factors that can cause downtime.


  • When a computer system shuts down or becomes inaccessible.
  • When storage shuts down, becomes inaccessible and unavailable.
  • Human error outage.
  • When data is corrupted (regardless of breadth of impact).
  • When an application slows down or stops processing.


  • Routine maintenance.
  • Data changes for performance enhancement and better manageability.

Factors That Lead to High Availability

Before implementing high availability solutions, it is essential to consider several factors:

  • The geographical location that surrounds the servers. If they are all in one area, they become more susceptible to problems like flooding and earthquake. Redundant servers should be distributed to different areas and datacenters.
  • Servers that are reliable and can withstand hardware failures, as well as power outage problems.
  • Software that is just as steady and resilient as the hardware.
  • Data should be safe even when failure happens.
  • A redundant network strategy.


High availability equates to reliability. It is beneficial for infrastructures or systems that put a high value on optimum operational performance. Ultimately, the goal is to increase functionality, efficiency and productivity.

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Photo courtesy of The U.S. Army.

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