Failover System in Cloud

Pre-requisite: Cloud Computing

The failover system technique makes use of established clustering technologies to provide redundant implementations in order to boost the availability and reliability of IT resources. When an active IT resource becomes unavailable, a failover system is set up to automatically transition to a redundant or standby instance of that resource.

Mission-critical software or reusable services that could create a single point of failure for several applications are frequently subject to failover systems. In order to host one or more redundant implementations of the same IT resource at each location, a failover system can cover more than one geographical area. To provide redundant IT resource instances that are continually monitored for the detection of defects and unavailability conditions, this approach may rely on the resource replication mechanism.

Configurations of Failover Systems

Active-Active

In an active-active setup, redundant IT resource implementations actively and synchronously support the workload (Figure 1). It is necessary to load balance among active instances. The failed instance is eliminated from the load balancing scheduler when a failure is discovered (Figure 2). Whenever a fault is discovered, the processing is transferred to the IT resource that is still active (Figure 3).

Figure 1: shows how the failover system monitors Cloud Service A and B operational conditions.

Figure 2: The failover system instructs the load balancer to transfer the workload to the redundant Cloud Service B implementation when a failure in one Cloud Service A implementation is discovered.

Figure 3: Failure of the Cloud Service After being duplicated from or recovered from an implementation, a cloud service is operational. The failover system has now sent the load balancer instructions to disperse the load.

Active-Passive

A standby or inactive implementation is triggered in an active-passive setup to take over processing from an IT resource that becomes unavailable, and the associated workload is directed to the instance taking over the operation.

Some failover systems are made to reroute workloads to operational IT resources. These systems rely on specialized load balancers to identify failure conditions and remove instances of failed IT resources from the workload distribution. This kind of failover system is appropriate for IT resources that support stateless processing and don't need execution state management. The redundant or standby IT resource implementations are required to share their state and execution context in technology architectures that are often based on clustering and virtualization technologies.

Figure 4: The failover system keeps track of Cloud Service's operational condition. In the Cloud Service, first Requests from cloud service users are being processed by an implementation serving as the active instance.

Figure 5: Service in the Cloud when an implementation serving as the active instance experiences a failure, the failover system notices it and switches to using the inactive Cloud Service. An implementation is made, and the workload is directed there. The most recent Cloud Service invoked The active instance has now been replaced with an implementation.

Figure 6: The unsuccessful Cloud Service A implementation is salvaged or copied into a working cloud service and is now designated as the standby instance, with the first invoked Cloud Service A continuing to function as the active instance.