A server cluster is a collective group of servers distributed and managed under a single IP address. This setup ensures higher availability, proper load balancing, and system scalability.
Each server is a node with its own storage (hard drive), memory (RAM), and processing (CPU) resources. This process is known as failover clustering.
Downtime can result in lost productivity and revenue. Not to mention performance disruptions that may lead to reputation loss. The real cost of outages, software failure, and outdated technology could mean millions. But the good news is that if you cluster server instances within an organization’s infrastructure, you can avoid these failures.
Why Are Server Clusters Deployed?
Businesses often deploy cluster servers to minimize downtime and maintain system accessibility, even when critical hardware fails. For instance, a two-node cluster configuration means that if one physical server crashes, the second will immediately take over, keeping downtime minimal.
Cluster server architecture is also ideal for businesses suffering from performance degradation. It lets them split off the database server to enable fast and uninterrupted performance for high-volume workloads.
What Are the Types of Server Clusters?
There are four types of server clusters. The type you choose depends on your business objectives and infrastructure needs. Let’s explore each more in depth.
1. High Availability (HA) Server Clusters
High availability (HA) clusters are an optimal choice for high-traffic websites. For example, you may use HA clusters for online shops or applications that need optimal, continuous performance from their critical systems.
High availability clusters let you avoid single points of failure since they are built on redundant hardware and software. They are critical for load balancing, system backups, and failover. These machines are composed of multiple hosts that can take over if a particular server shuts down, guaranteeing minimal downtime if a server overloads or fails.
HA Server Architecture
HA clusters have two architecture types: active-active and active-passive.
An active-active cluster means all nodes work simultaneously to balance loads. In contrast, an active-passive architecture means a primary node handles all workloads. Meanwhile, a secondary node remains on standby for downtime.
The secondary server is also known as a hot spare or a hot standby since it contains the database from the primary node. As the hot standby is ready to take over if a component crashes, this is a lower-cost implementation than active-active.
High availability clusters give you more reliability while also letting you scale easily. Not to mention, they offer more efficient maintenance and robust infrastructure security. With these clusters, you can save costs, minimize downtime, and create a better user experience.
2. Load Balancing Clusters
Load balancing clusters are server farms that distribute user requests to multiple active nodes. The main benefits include accelerating operations, ensuring redundancy, and improving workload distribution.
Load balancing lets you separate functions and divide workloads between servers. This configuration helps maximize the utilization of resources. It uses load balancing software to direct requests to different servers based on an algorithm. The software also handles outgoing responses.
The active-active configuration of a high availability cluster uses load balancers. The HA cluster uses the load balancer to respond to different requests and distribute them to independent servers. Depending on the configuration data and computer performance, the distribution can be symmetrical or asymmetrical.
In an active-passive high availability cluster, the load balancer monitors nodes’ availability. If a node shuts down, it doesn’t send any more traffic until it is fully operational.
Load balancing architecture also lets you use multiple links at the same time. This feature is especially useful in infrastructure that requires redundant communication. For example, telecommunications companies and data centers often deploy this architecture. The main benefits include cost reduction, high-bandwidth data transfer optimization, and better scalability.
3. High-Performance and Clustered Storage
High-performance clusters, also known as supercomputers, offer higher performance, capacity, and reliability. Businesses with resource-intensive workloads most often use them.
A high-performance server cluster is made up of many computers connected to the same network. And you can connect multiple such clusters to the network’s data storage centers to process data quickly. In other words, you benefit from high-performance and data storage clusters and get seamless performance and high-speed data transfers.
These clusters are widely used with the Internet of Things (IoT) and artificial intelligence (AI) technology. They process large amounts of real-time data to power complex projects such as live streaming, storm prediction, and patient diagnosis. These attributes of high-performance cluster applications also lend themselves well to research, media, and finance.
4. Clustered Storage
Clustered storage consists of at least two storage servers. They let you increase your system’s performance, node space input/output (I/O), and reliability. Depending on business requirements and storage demands, you can opt for a tightly or loosely coupled architecture.
A tightly coupled architecture is directed at primary storage. It separates data into small blocks between nodes.
In contrast, a self-contained, loosely coupled architecture offers more flexibility. But it doesn’t store data across nodes. In a loosely coupled architecture, performance and capacity are limited to the capabilities of the node storing the data. Unlike tightly coupled architecture, you can’t scale with new nodes.
How Does Server Clustering Work?
Each cluster server is a node with its own memory, storage, and CPU resources. The same image of the server’s operating system and core applications on each node is what bonds them together.
Typically, not all nodes within the cluster operate at the same time. One node will be operational, while the rest of the nodes within the server cluster will be in standby mode. If the active node can’t handle incoming traffic or fails to carry out a server request, the cluster will redirect that query to another node. This balancing of the cluster’s workload makes website or app downtime virtually non-existent.
How Do Server Clusters Provide High Availability?
Ideally, you use multiple web and app nodes to guarantee hardware redundancy. We call this kind of architecture a high availability cluster. It helps prevent downtime if a component fails. This is especially true if the operating system fails, which does not have redundancy in a single server. Since there will be no site failures, your users will not even know that the server crashed.
Specifically, HA clusters will leverage an active-active (or load balancing) server configuration to ensure the system can swap resources without any service interruption. Although more effective, this configuration typically costs more than an active-passive (or hot standby) configuration since all nodes within the system must stay active.
How Do Server Clusters Provide Load Balancing?
Server clusters provide load balancing by seamlessly switching excess workload to other available nodes within the system. This can be done through either an active-active or active-passive setup.
As incoming traffic or data processing queries exceed the limit of one server, they can be swapped to another available cluster server. Typically, this switch can happen in two ways — manual and automatic.
Manual clusters are not an ideal solution since the manual configuration of a node to the same data IP address comes with downtime. Even a two- to five-minute downtime could be expensive or possibly critical. On the other hand, automatic clusters let you configure software ahead of time. This type of cluster setup automatically carries out the server switch.
How Do Server Clusters Provide Scalability?
Server clusters provide scalability horizontally within the system. IT teams can easily add subsequent nodes (or computers) to accommodate the amount of traffic or data transmissions they see fit.
Additionally, just the existence of extra servers increases scalability. Only one server is necessary to run business processes. The extra servers in the configuration allow flexibility and scalability with resources, which can improve fault tolerance and performance.
Benefits of Server Clustering
A clustered environment helps you manage hardware, application, and website failures. In other words, this environment ensures uptime and availability. By saving engineering efforts, it can drastically reduce costs associated with system recovery. Put simply, investing in server clusters helps your business grow in the long run via the following benefits.
Flexibility and Scalability
An individual server handles everything from the network connection to storage for a business. By deploying a multi-server architecture with clustering capabilities, you can significantly improve the flexibility and scalability of that server.
In other words, clustering lets you scale one server to handle the increasing resource demand. Not to mention, it's simpler for businesses to deploy an additional node to an existing cluster. If you have dedicated server hosting, you can do so with a simple phone call.
Improved Availability and Performance
Another motivation-driving investment in cluster server systems is performance. Besides providing hardware redundancy and ensuring uptime, a clustered environment can improve performance.
In particular, a cluster with a dedicated database server can improve website or application speed by offloading database-related tasks onto a specialized server. This setup lets you improve performance while increasing support for simultaneous connections.
If you comply with regulations such as PCI DSS (Payment Card Industry Data Security Standards), server clusters become a practical necessity. This is especially relevant if you store financial information on a server that doesn't connect to the Internet.
Reduced IT Costs
Companies need a network with built-in redundancy to ensure customers can always connect. Besides that, the servers need to act as a single system. A clustered environment helps prevent downtime and lower costs by keeping the server fully operational.
In other words, clustering lets you provide continuous uptime. As clustered servers work together on a single network, they reduce risk vulnerability while boosting network performance.
Clustered server architecture can benefit businesses of all sizes. Specifically, it helps optimize processes, from networking services to the end-user experience. All these workloads are assigned to applications and rolled out on separate servers that sync in real time.
A business can customize the number of servers in a clustered environment. This customization allows for cost management while eliminating single points of failure. Using custom-built infrastructure ensures your environment is engineered for your workload. Working with a reputable service provider is a great way to determine the most cost-effective architecture for you.
The True Cost of Downtime
Are cluster server systems really that beneficial? How costly can downtime truly be to your business?
Well, according to Uptime Institute’s 2022 Outage Analysis Report, 80% of organizations report their data centers have experienced some outage over the past three years. For 60% of those outages, total financial losses were $100,000 or more. An unlucky 15% of respondents reported outage costs upward of $1 million. But, besides financial losses, businesses reported facing reputational damage and compliance breaches.
Notably, in October 2021, Facebook’s network was unavailable for six hours. This network failure resulted in an estimated revenue loss of $99.75 million before users could get back online. That’s a loss of over $16 million per hour.
Now, most businesses won’t lose as much revenue as Facebook. However, rising hourly downtime costs persist and require serious consideration. If your business requires reliable IT services, consider server clusters. They are a critical investment for long-term growth and performance. A clustered environment will boost performance and ensure infrastructure availability, scalability, and reliability.
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Melanie Purkis is the Director of Liquid Web's Managed Hosting Products & Services. Melanie has more than 25 years of experience with professional leadership, project management, process development, and technical support experience in the IT industry.
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