As the demand for server speed and reliability increases, the need to implement a reliable server cluster to ensure maximum performance is paramount. With a tightly integrated cluster of multiple servers working in tandem, you’ll be able to offer robust services that are resilient, consistent, and provide uninterrupted performance.
Server clusters are key to offering great business service availability while controlling costs at the same time. Learn some of the key benefits that come with utilizing a server cluster.
Server Cluster Benefits and How They Actually Work
A server cluster is a group of servers all tied to the same IP address. They might provide access to files, printers, messages and emails, or database records. Each server on the cluster is called a node, and each node can run independently as it has its own CPU and RAM and either independent or shared data storage.
The main advantage of server clustering is better uptime through redundancy. If one node in the cluster – one server – fails, the others are fully capable of picking up the slack almost instantly. User access is essentially uninterrupted, and unless the server cluster was already substantially under-resourced, there should be no performance issues at all for the expected user load.
Benefits of Using Server Clusters to Power Mission-Critical Applications
Server clustering is used in a variety of hosting environments. That is to say, server cluster benefits are not exclusive to mission-critical applications. However, their chief benefit is that they are not subject to a service interruption from a single server node failure. This is kind of the holy grail for a mission-critical application.
Similar benefits can be had from operating a backup server, either on- or off-site. However, there is almost always a noticeable failure of service while transferring to the backup, and the possibility of data loss is high, especially where the server is often not backed up continually.
Strategies for Ensuring Maximum Performance, Reliability, and Availability
The key server cluster benefits are reliability and availability. However, there are many ways to achieve these two goals and many strategies for maximizing reliability and availability with other factors, especially cost.
There are essentially two types of server clustering strategies – the traditional strategy and the shared-nothing strategy.
Traditional server clustering sees multiple redundant server nodes accessing the same shared storage or SAN resource. If a server node fails or experiences downtime, the next node picks up immediately, and as it accesses the same storage, there should be essentially zero data loss. If the failure happens in the SAN, though, there are problems.
Shared nothing server clustering sees each node having a completely independent data store, essentially a hard drive. These drives are generally synchronized at the block level and are effectively identical from moment to moment. If a failure occurs anywhere in the cluster, another node can take over completely from its own hard drive.
Cluster Protection Against Failures and Outages
The core defense that server clustering provides against service outages is a redundancy of components. For example:
Application and Service Failure
Application or service failures often result from critical errors in the software the server is running. Clustering can help by running multiple independent copies of the software.
System and Hardware Failure
If a physical fault or failure develops, it will generally only affect one node of the cluster. The other node or nodes can take over.
Site failures generally happen to the entire data center, either from power disruption, natural disasters, or human error. Clustering could only protect against a site failure if one or more of the nodes of the cluster were located on a different site – something which can be expensive and inefficient but is quite achievable.
Security Considerations When Deploying a Server Cluster
With all the server cluster benefits on offer, it is easy to forget that all servers are potentially vulnerable. You need to address the same security concerns when setting up a clustered server as with any other:
- Use a good firewall.
- Keep your OS updated.
- Secure data moving to and from the cluster.
- Use a strong authentication procedure.
- Physically secure the servers.
- Consider encrypting the file system.
Different Types of Server Clusters
Going deeper into what server clusters are, it’s time to explore each of the main types of clustered server arrangements.
Basic Clustered Storage
These are your bread-and-butter clustered storage solutions without any of the bells and whistles. They work perfectly well for most purposes and are low-cost.
High Availability (HA) Server Clusters
These are usually shared storage clusters and may be composed of virtual machines running on a single host. They maximize uptime but can compromise reliability slightly.
Load Balancing Clusters
These clusters use a load balancer or cluster switch to, as you might imagine, balance the load of incoming requests across several nodes running all at once. It optimizes for service speed rather than uptime or reliability.
High-Performance Clustered (HPC) Storage
An HPC cluster uses top-of-the-line hardware in each node of a large cluster and the fastest interconnect available. It maximizes performance, but by doing so mostly at the hardware level, it generally does not compromise reliability or availability. Often, all three are higher than standard clusters.
Cost Savings & Other Advantages of Server Clustering
One of the most important server cluster benefits on a practical level is the reduced IT costs customers generally realize. Less downtime simply costs less in the end, even with a more expensive setup.
Other advantages include higher flexibility, scalability, performance, and availability, as well as a more easily customizable server infrastructure.
Server clustering is a very effective strategy to ensure your most mission-critical data resources provide all the uptime you need. There are several ways to tweak the cluster architecture or hardware to focus on specific advantages, but almost all server clustering strategies offer improved performance, uptime, and reliability. It is a question of choosing the best of several good options, a type of problem the IT industry sees far too little of.