Why Redundancy in Systems is Critical

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If you ever come across engineers, they might dabble on about the significance of redundancy in systems. This technical jargon will of course mean nothing to the rest of us – so let’s get started in understanding why it is a critical element to any system.

Understanding Redundancy

In simplest of terms, redundancy is a backup; much like a spare tire, or perhaps a second job.

In engineering, the term refers to the addition of extra components to a critical system – this helps in ensuring that in the scenario that a mishap takes place, the chances of failure are largely reduced since a second option is available. 

Some examples of redundancy component types are:

  • Back-up controls
  • Back-up power systems (such as in airplanes)
  • Extra hard drives and critical information system components. 
  • Additional power supplies in computers in data centers

The internet also utilised the concept by applying it to it’s system maintenance procedures. How so? 

Think about websites and the many individual links that form a complete website. Does the failure of one single link bring down the whole site? Even if one link fails to operate in an optimum manner, the rest of the site does not come crashing down as it has been designed in such a way so as to withstand minor failures; in other words, the concept of redundancy has been applied. 

Types of Redundancy

While many different models and techniques are applied, the more frequently applied methods across various industry are: 

1. Standby Redundancy

Standby redundancy refers to instances where a secondary unit is kept on standby, to be used

if the need arises. Understandably, it is also referred to as Backup Redundancy.The two units are

referred to as primary and secondary; and are usually houses separate. Due to this, they are not in

sync and upon transfer to the standby unit, a “bump” might be experienced in the flow of work.

Standby redundancy has two sub-types:

  • Cold standby

In cold standby, the secondary unit is kept powered off. However, due to its sedate 

state, switching over to the standby requires more time and effort, as it first

first needs to be brought to an active state. 

  • Hot standby

Hot standby design significantly reduces the downtime experienced during a cold

standby since the secondary unit is powered and ready to go.

Additionally, in standby redundancy, a third party or watchdog unit is required to keep an eye on the situation and determine when a switchover needs to be made. This problem can be eliminated in hot standby by having the secondary unit assume the role of the watchdog and thus being able to determine when to switch to the secondary unit. In engineering-reliant systems such as roller coasters and amusement park rights, the watchdog tasks may undertaken by a combination of human operators and computers.

2. N Modular Redundancy

N Modular Redundancy is able to significantly reduce the takeover time. This type of 

redundancy is also referred to as parallel redundancy; as this employs different units that are

running simultaneously. This means that a switchover would be largely seamless, and downtime

would be insignificant.

In N Modular Redundancy, there are three main sub-types:

  • Dual Modular Redundancy
  • Triple Modular Redundancy 
  • Quadruple Redundancy 

However, a major drawback is also that in case of failure, the entire system might fall apart.

While aircrafts with multiple engines primarily employ them to bear the power requirements of

the flight, these engines de facto function as N Modular Redundancy components by keeping the

systems running in case of unit failure.

3. 1:N Redundancy

1:N redundancy is the type of redundancy where a single backup system is maintained

for multiple systems. In case of failure, the backup can operate for any one of the primary

systems. While the cost is considerably lower in this practice, the risk is quite high. 

Why is Redundancy so Important?

Redundancy in systems holds considerable importance and are a critical component of risk management practices. Here are some of the reasons why:

  • Improved reliability

Reliability is the probability of not failing in a particular environment and at a specific time.

Having backup understandably reduces the chances of temporary failure; which can have dire

effects: including accidents and losses.

  • Increased availability

Availability of a system is simply the percentage of time that an application was up and running

in comparison to it’s recorded downtime. With redundancy, downtime is reduced to a large

extent, as only a switchover is required, as opposed to a system without redundancy where the

fault would need to be detected, fixed and tested before the system goes live again/

Applications outside engineering

The concept of redundancy has widespread implications. It surpasses the scope of engineering and is applicable to all areas of business, work and lifestyle management. Applying redundancy to systems being encountered in everyday life would open the doors to multitudes of opportunities and enhanced efficiency. Examples of redundancy beign employed in every day life include:

  • Secondary mobile phone with back up data
  • Planning secondary sources of income
  • Standby Fire Truck for Emergencies
  • A backup player in case a superstar is injured for a game.

Reference Links

http://www.ni.com/white-paper/6874/en/
http://www.icsenggroup.com/types-of-redundancy.shtml

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