The concept of failing over critical services provides an extremely powerful way to maintain business continuity, even when a disaster occurs. It allows organizations to have continuous network service operation during a failure. Cloud failover is a new trend allowing businesses to have failover instances in the cloud, which they can failover to in the event of a disaster.
Using multiple servers, especially in an active-active or active-passive configuration, makes the service resilient if an outage is experienced. It can help prevent data loss due to a single point of failure.
What is Failover?
A failover solution refers to the automatic transition of services, tasks, or operations from a primary system or server to a secondary system or backup when the primary one encounters a failure. This process is critical in maintaining uninterrupted service availability, especially in network environments and cloud services.
Failover can handle hardware failures, software crashes, or network connectivity issues. It allows rerouting the workload to the secondary system until the primary one can be restored. This ensures that users or clients experience minimal downtime during such events.
With today’s virtualized infrastructure, failing over generally means shifting traffic from one set of virtual machine workloads to a secondary set of VMs that have been replicated from the primary environment. If these are containerized workloads, it will mean you have additional container hosts in the secondary site.
What is Cloud Failover and How is It Different?
Cloud failover applies the same concepts of traditional failover, except it leverages cloud resources for the secondary environment. Cloud failover allows companies to be able to switch automatically to the secondary environment in the cloud rather than using a secondary on-premises data center.
While traditional failover might transition services between two servers in the same physical location, cloud failover can involve switching services between different geographical locations. This scalability and flexibility offered by the cloud ensures even higher availability and resilience against a wider range of disasters.
Load Balancing
One way organizations can achieve better application performance and redundancy is by using the concept of load balancing. Load balancing at the network layer evenly distributes incoming network traffic across multiple servers. The load balance concept ensures no single server is overwhelmed with traffic.
It can also be a core high availability component, ensuring services remain uninterrupted. If a failure is detected, the load balancer won’t send traffic to the failed component and all requests will be served by the healthy components of the system. To scale the solution, you add more nodes to the configuration, allowing more redundancy.
DNS Failover
DNS has been described as the “phone book” of the Internet. It allows looking up the IP address associated with a friendly name. Applications are generally written to reference resources found based on DNS records.
DNS failover directs user traffic from a failed server to a healthy one. It involves having DNS determine which server a client should access based on server health and other criteria. This way, even if a primary server is down, the user is automatically redirected to a secondary failover server.
During a failover, DNS record IP addresses are changed to reflect the IP addresses of the secondary environment instead of the primary servers. With this change, applications seamlessly redirect to a healthy environment rather than the primary one experiencing failure.
Active-Active vs Active-Passive Configurations
In an active-active configuration, all servers or nodes in the cluster share the workload equally. They’re all “active” in serving client requests. In active-active configurations, data is synchronized in real-time across all the nodes. This way, the data is always up-to-date, no matter which node is serving out the application.
In a failure with active-active nodes, you will have up-to-date data since the remaining nodes are synchronized. With active-passive configurations, there may be a skew of data or data loss between the primary and secondary configurations.
This is because the passive nodes may synchronize data at a specified interval. It means the business is ok with a certain amount of data loss, since the most recent replication interval may not have happened when the disaster occurs.
Active-passive configurations mean the secondary set of resources is in “stand-by” mode, meaning they are not actively serving out resources until they are told to do so.
Fault tolerance
Fault tolerance is a concept that usually combines different components of failover, such as DNS failover and load balancing. By this combination, the chances of application downtime are reduced dramatically. Systems can be designed to automatically switch to a backup or a failover server when it detects an issue with the primary system.
How are Virtual Machines involved?
Virtual machines have opened up many possibilities regarding disaster recovery and site-level fault tolerance to bolster cloud failover strategies. Since virtual machines are abstracted from the underlying physical hardware, they offer a flexible way to replicate services and data across different servers and clusters, helping to ensure high availability.
Failback operations
Failback operations are extremely important. After all, once a disaster scenario has been resolved, equipment has been repaired, or the disruption has been removed.
After a failure, the system must revert, or “failback,” to the original location or primary server once it’s operational. Failback operations ensure the workload returns to the primary site after fixing the primary server.
However, this may not be a trivial operation since all the data and changes captured in the secondary environment must be replicated back to the primary data center, servers, and storage.
Frequently asked questions
How does a scale-out backup repository differ from traditional backup storage?
A scale-out backup repository is a modern approach to data storage that combines multiple storage devices into a single pool. Instead of relying on a single storage system, it allows you to aggregate multiple repositories, including object storage, to handle large volumes of data more efficiently. This architecture enhances both performance and scalability, adapting to growing backup needs.
Why is the cloud tier essential in backup infrastructure?
The cloud tier is an offsite backup, ensuring data security even during local disasters or hardware failures. By moving backup data to a cloud tier, businesses can leverage the scalability and cost-effectiveness of cloud storage while ensuring a higher level of redundancy and disaster recovery preparedness.
What’s the role of backup copy jobs in the backup process?
Backup copy jobs are essential for creating secondary copies of backup data. By creating these secondary copies and moving them offsite, such as to a cloud tier, businesses enhance their data protection strategy, ensuring that even if the primary backup fails or becomes corrupted, the secondary backup remains intact and accessible.
How do backup repositories ensure data compliance, like HIPAA or ISO 27001?
Backup repositories often have built-in encryption and security measures that ensure data remains secure in transit and at rest. Using modern encryption standards and offering features like object lock or insider protection, backup repositories can meet various compliance standards, including HIPAA, ISO 27001, and more.
How do local repositories differ from cloud backup repositories?
Local repositories refer to backup storage within the business premises or data centers. They offer quick backup and restore times due to data locality. Cloud backup repositories, on the other hand, are offsite storage solutions. While they might have slightly longer restore times due to data retrieval from the cloud, they offer enhanced redundancy and provide protection from disasters.
Wrapping up
Using cloud technologies has become a de facto standard as part of the disaster recovery strategies for modern organizations. Leveraging cloud failover provides many benefits, allowing organizations to assume all the benefits of cloud infrastructure as part of their failover capabilities.
Read More:
MSP Series: Choosing Backup as a Service (BaaS) Provider : Part 16
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