Failover Testing

Failover Testing: There may be a case when the server is expecting heavy traffic and has heavy use and heavy traffic at peak times involving lots of data transfer. In such scenarios, it may happen that the available server may become unable to render service to all the requests that come to it.

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This problem must be solved; otherwise, the server may crash, become inactive, or get hung for a long time. To prevent such scenarios from happening in real life, there is a need to do Failover testing in order to prevent disaster due to the Failover system.

Failover testing verifies whether the system can continue daily operation with the increased load at peak times and recognizes that a need has arisen to allocate additional resources in the scenario when the system cannot handle the traffic without additional resources.

Let us make it more clear with one example. Let us suppose that 4 web servers are undergoing heavy load, and one of them crashes due to heavy load; then there is a need to see whether the Load Balancer is working as per expectation and whether the three web services are capable enough to handle the load or does it require manual help or whether the notification is sent to right people at the right time to recover from such situation.

In Failover testing, we need to see everything related to recovery and working as expected to recover from such scenarios.

Importance of Failover testing

Apart from load balancing, Failover testing also helps determine the resource’s future requirement for load balancing and sets the benchmark for the future. Also, by setting the load balancing, the system can bring down any server for maintenance without the downtime and impacting any operation by moving operations to the backup system.

They maintain the existing system and allocate extra resources to prevent system failure after the system reaches the threshold value of the load, after which the system is bound to crash if the required external resource is not allocated to the system. The extra resource here means an additional CPU or server is required to maintain the continuity of the operation without any downtime.

Another thing to note is that Failover testing is part of performance testing and is very important when doing performance and capacity planning.

Factors considered for doing Failover testing

Some applications are critical, and scheduling downtime in such applications can greatly harm the client’s business. For doing Failover testing, there is a need to schedule downtime. Therefore, many factors are to be considered before scheduling downtime in order to do Failover testing, some of which are given below:

  • Loss to the company during the scheduled downtime
  • Cost to prevent the system from breaking Down
  • Duration of the downtime
  • Probability of system failure

Let us discuss these points in brief

  • Loss to the company during the scheduled downtime: There will be a business loss to the company during the scheduled downtime, and the whole operation will be interrupted due to this downtime.
  • Cost to prevent the system from Breaking Down: it means when the system reaches the performance threshold where the system is bound to break, there is a need to allocate extra resources to prevent the system from Breaking Down, such as adding a CPU or server to maintain the balance and share the load so that operation is continued. The cost will be associated with allocating extra resources, which will also be considered before Failover testing.
  • Duration of downtime: No client would like the operation interrupted for a long time. So, if downtime is longer, the client is less likely to approve Failover testing.
  • Probability of system failure: If the probability of system failure is much less, almost zero, then in this situation, the client is less likely to approve Failover testing.

How to perform Failover testing

  • A Failover testing plan should be done regarding performance requirements that will be there in the coming future or are already required.
  • Set up suitable benchmarks to meet the performance requirement
  • Prepare test plan as per market requirement
  • Execution of the test plan
  • Preparation of report regarding issues or resource requirement

Things that require special attention while doing Failover testing

Proper backup and restore mechanisms should be in place before doing Failover testing. There should be a proper backup of data so that the same data can be restored if any problem occurs during the Failover testing. Also, a proper mechanism should be used to handle system failure or crashes while taking data backups.


Overall, we can say that the main purpose of Failover testing is to, first of all, identify the phase at a particular load where the system stops responding and allocate extra resources to that system so as to provide support to the system in handling the load by sharing of load or taking a whole load of extra resources, in case required. So, we can say that Failover testing aims to build a stable and robust system to provide continuous service without any failure.

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