[Defined] What Is Failover Cluster or High-Availability Cluster? [MiniTool Wiki]
What Is a Failover Cluster?
A failover cluster is a group of independent computers that work together to increase the availability and scalability of clustered roles. They were known as clustered applications and services before. The clustered servers, also named nodes, are connected by physical cables and software. If one or more of the clustered servers fail, the other servers start to offer service; this process is called failover.
Besides, the clustered roles are proactively monitored to verify that they are working properly. If not, they will be restarted or removed to another node. Also, failover clusters provide Cluster Shared Volume (CSV) functionality that offers a consistent, distributed namespace that clustered roles can use to access shared storage from all nodes.
With the failover clustering feature, people experience a minimum interruption in service. Failover clustering has a lot of apps such as:
- Highly available clustered roles that run on physical servers or virtual machines installed on servers running Hyper-V.
- Highly available or continuously available file share storage for apps like Microsoft SQL Server and Hyper-V virtual machines.
A failover cluster is also referred to as a high-availability cluster sometimes.
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What Is a High-Availability Cluster?
A high-availability (HA) cluster is a group of computers that support server applications that can be reliably used with a minimum amount of downtime. It is also called HA cluster or fail-over cluster. They operate by using high availability software to harness redundant machines in groups of clusters that offer continued service when system components fail.
Without clustering, if a server running an important program is down, the program will be unavailable until the crashed server is fixed. High-availability clustering avoids that situation by detecting software and hardware faults and restarting the target program immediately on another healthy server without administrative intervention. This process is known as failover.
What Does Failover Cluster Do?
Usually, failover clusters are used for critical databases, business apps, file sharing on a network, as well as services such as electronic commerce websites. Its implementations attempt to create redundancy into a cluster to eliminate single points of failure, including multiple Internet connections and data storage which is redundantly connected via SAN (storage area network).