What is a single point of failure?

This is a component of a system, process, or business where there is no redundancy, so a failure at this point would bring that system, process, or business down.

A dramatic example of a single point of failure would be the engine in a single engined aeroplane. 

For example, a single point of failure in your computer network might be the hard disk in your PC. That is why servers have multiple disk drives. Of course the actual server itself is a single point of failure, but entire servers can now be made economically redundant. 

Modern technology allows us to create systems with far less single points of failure and fast recovery options for any that exist.

Effectively single points of failure are usually mitigated through multiple redundant components. Where it is not possible, practical, or economical to use a redundant component, a single point of failure can have less impact if an alternative, often less expensive component can be used in lieu of the failed component to maintain service whilst the critical component is replaced.

Having backups in your computer network is critical to your business as your software is also a single point of failure. People who operate the systems may also cause data loss through user error. Also, your entire office is a single point of failure. You could have a fire, or lose everything through theft. The harm from this can be minimised by keeping data backups off site.

Cloud computing is often touted as a way to avoid single point of failure. Vendors explain at length how they have redundant this and duplicate that. If you can back up all of your data AND programs to a location outside of a cloud provider, you omit the single point of failure that is your cloud provider. If they fail, you can restore your systems to another cloud provider, or your own equipment.

However, some cloud providers don't let you back up to your own media? Some vendors sell software as a service, where even if you have your data backed up, there is no way to access the software that is used to access your data? If these applications are the life blood of your business, a failure of the vendor is one that many businesses may not be able to recover from. 

No matter how you operate your business, think about single points of failure and ensure that you have a way to recover from them, or you may find out when it is too late, that you have just lost your business altogether.