What is Failover?
Failover is a backup operational mode that automatically switches to a standby database, server or network if the primary system fails, or is shut down for servicing. Failover is an extremely important function for critical systems that require always-on accessibility. Failover functionality seamlessly redirects requests from the failed or downed system to the backup system that mimics the operating system environment.
System designers create failover capability in servers, backend database support, or networks with a need for constant availability and exceptional reliability. Failover can:
- Protect your database during maintenance or system failure. For example, if the main server onsite suffers a hardware failure, the backup server (onsite or in the cloud), can immediately take over hosting responsibilities without manual input.
- Allow maintenance jobs to run automatically without the need for supervision. An automated switchover during scheduled software updates allows for immediate and seamless protection against cyber security risks.
- Be completely customized to suit your hardware and network configurations. While maintaining a database, an administrator can have not only an A, B system of two servers running in tandem to protect each other against failure, but also can use a cloud server as well to allow for full on site troubleshooting repair and updating, all without connectivity issues.
Failover can apply to any aspect of a system:
- On a personal computer or mobile device, a hardware or software trigger can protect the device when a component, such as a processor or even a battery cell fails.
- Within a network, failover can apply to any individual network component, even a system of components, such as a connection path, storage device, or Web server.
- With a hosted database or web application, failover is what allows multiple local or cloud based servers to maintain a constant and secure connection with little or no interruption of service.
Failover as a service is functionally similar to switchover, the difference being that failover can occur automatically and without warning, while switchover necessitates human intervention in order to start. Switchover often occurs when an administrator wants to apply hardware or software updates, bug fixes, or feature testing, to either the main or backup system without terminating connectivity for the user.
At the server level, failover automation often incorporates a heartbeat system. This system, in basic terms, connects two servers either physically through a cable or over a wireless network. As long as the pulse between the two servers continues uninterrupted, the second server will not go online.
Often, depending on the complexity of the hosting, a system might even have a third server that is running the basic components required to prevent any downtime during switching. The heartbeat communication exists between the two servers as a way of keeping the second server ready to switch over if needed. Multiple paths, redundant components, and offsite or cloud-based support all help to assure a secure and always connected pathway.
A systems administrator will sometimes build an automated notification signaling to users that a switch has taken place. Alternately, some systems will notify the working technician of a need for switchover. They can then manually initiate the switch to the secondary server. This is called automated with manual approval configuration.
The increased prevalence of virtualization software has changed failover’s reliance on physical hardware. This has been possible because of migration, in which an active virtual machine is transferred from one physical host to another, allow for a completely smooth continuation of service.
Why Failover is Important
Failover and its systems give customers comfort in knowing that they will be able rely on a secure and protected connection, without unforeseen interruptions. Failover integration may seem like an unnecessary financial burden, but is in fact an important insurance policy that provides safety and security.
Failover’s main purpose is the stopping of, or at the very least the reduction of, complete system failure. Fallover, the term used to describe customer impact of systems failure, is an important measure of a business’s reliability as a service. Failover is an integral part of any businesses disaster recovery plan. If the network infrastructure is configured correctly, then failover and failback will be a seamless and total safeguard against most if not all service disruption. Any hiccups of real measure are usually caused by the size of the data changeover occurring, the available bandwidth, and how the data is being transferred, mirrored or replicated to the second location.
For a systems engineer, the focus should be on minimizing data transfer while maximizing the quality of synchronization between the two sites. After securing data transfer quality, the next concern is how to trigger failover while reducing the change-over time.