Learn the major types of server hardware and their pros and cons

What is a server?

A server is a type of computer that provides processing and memory resources for different workloads. The term server can refer to the computer itself or to a program that delivers a service, such as an email management system. Most hardware-related references concern the physical machine. The server operating system (OS) is designed to process large workloads, deliver services and support network-based operations. Common server OSes include Linux, Unix and Windows Server.

Servers are usually set up to provide one or more specific services. Servers are commonly used to manage network resources and make them available to client devices. A server is often referenced to based on the purpose it serves. For example, a print server provides network users with access to shared printers, and a media server streams video and audio content to network users.

A server's physical configuration is usually specific to the types of services it provides. For example, a database server might include more processing or memory resources to handle the influx of concurrent transactions. Many data centers also implement server virtualization to deliver services more efficiently. Server virtualization can help better utilize the server's physical resources, while also increasing flexibility and security and reducing energy consumption.

Why purchase a server?

Any organization that supports more than a handful of users can benefit from different types of server hardware. For most organizations, servers are essential to carrying out business and protecting sensitive resources. Organizations might need to purchase servers when they set up new data centers, expand or update existing ones, open satellite offices, or spin up development projects.

Although servers add to the number of computers that an organization must support, they can also help consolidate resources; different types of server hardware make it possible to share printers, disk drives and applications with network users. Although users can share resources across peer-to-peer networks, a server is much better equipped to manage those resources and deliver them securely across the network, especially with a large number of users.

This use of servers can also lead to greater productivity because resources are centralized, which allows workers to easily share data with their colleagues. Users can access the resources they need when they need them without worrying about managing them. For example, they do not have to keep a copy of the data on their own systems, implement and maintain a backup, or manage multiple copies of the same data.

In addition, servers enable users to access the applications and data they need from remote locations, which makes it easier for workers to stay productive when they travel or work remotely.

Servers also add business value via data protection, providing the structure necessary for admins to control which users can access files, applications, peripherals and other resources. In addition, admins can control the security mechanisms that they implement on the servers, as well as centrally monitor systems for issues related to security and compliance.

Different types of server hardware also make it easier to back up system and user data and implement disaster recovery strategies. Admins can also more easily ensure the reliability and availability of data, whether by clustering servers or building redundancies into system components. In addition, the consolidated model makes it possible to centralize other management operations, such as maintaining workstations, controlling domains and monitoring software.

Because servers can consolidate resources, streamline management and increase productivity, they can ultimately reduce costs. In addition, their centralized management capabilities make it easier to track application usage to better control licensing costs and avoid expensive software audits.

Because servers better protect the data, it is less likely to be compromised, helping to avoid costly fines, tarnished reputations and the lost business that comes with both of these.

Rack servers

A rack server, also known as a rack-mounted server, is a standard-size computer designed to be mounted in a server rack along with other rack servers or standard-size components, such as network or storage area network devices. A rack server is considered to be a general-purpose machine that can support a wide range of workloads.

Rack servers take up a lot less space than tower servers because they're not encased in bulky cabinets and users can stack them in a single rack along with the other components. In addition, because providers have standardized the size of racks and rack servers, admins can easily add or replace servers if one should malfunction. The design also makes it simple to add components gradually to accommodate growing workloads. Best of all, the servers in the same rack don't have to be the same model or come from the same vendor.

One of the biggest challenges with rack servers is managing all the cabling that ties the components together. Rack servers require cables for power, networking, management and storage, all of which hang off of the back of the stacked components, making it difficult to manage the cables and servers. The cables can also affect cooling, which is already challenging with rack servers because of their proximity to each other.

Blade servers

A blade server is a modular component -- blade -- that fits into a server chassis along with other blades. Each blade has its own processors, memory and integrated network controllers. The blade might also include a Fibre Channel host bus adapter, as well as other I/O ports. Blade servers offer more processing power in a smaller space than rack servers while providing a simplified cabling structure.

Because blades are so tightly configured within the chassis, the chassis itself is sometimes referred to as the blade server and the individual blades are called modular motherboards or circuit boards even though they're servers in their own right. This is because the chassis provides consolidated resources such as power, cooling and networking, which are shared across all the blades within the chassis. Admins can also mount the chassis on a standard-size server rack.

One of the biggest advantages of a blade server compared to a rack server is its ability to provide greater processing density within a smaller space. This can result in a price-to-performance advantage even though blade servers are themselves more expensive than rack servers. This efficient use of space can increase redundancy to better ensure the reliability and availability of applications and data.

In addition, the blades and chassis components are hot-swappable, including the cooling system, controllers and switches. Plus, because of the chassis structure, cabling is simpler when compared to the rack server. The blade system also provides a centralized management console to control and monitor the system's components.

Although blade servers offer state-of-the-art computing capabilities, they also come with a few drawbacks. For example, the server chassis and blade architecture are proprietary, which makes vendor lock-in a strong possibility. This proprietary nature can also limit upgrade options if the vendor does not release new or updated components in a timely manner.

Although blade servers are more expensive than rack servers, savings in space, power and management can offset expenses under the right circumstances. However, the rack server provides a lower entry cost, which can be an advantage to an organization that wants to start out small and work its way up gradually. Also, with blade servers, an organization might need to update its data center to accommodate power and cooling needs.

Despite these concerns, a blade server can be a good fit in a number of circumstances, particularly for data centers with high-density server rooms in which space is limited. Blade servers are well-suited to a single task that requires clustered servers, such as file sharing, web hosting, video streaming, database management or virtual desktop infrastructure.

Mainframe servers

A mainframe server is an extremely powerful computer; it's about the size of a large refrigerator. Unlike its predecessors, which could take up an entire room, today's mainframes are much more compact and powerful and include sophisticated encryption capabilities, as well as multiple layers of redundancy. Mainframes are still much bigger and bulkier than rack or blade servers, as well as a lot more expensive. However, mainframes are also much more powerful and reliable than anything else out there.

A mainframe is designed for high throughput; it can support a large number of simultaneous transactions and heavy I/O loads without affecting performance. IBM leads the way in the mainframe market, producing systems that can perform 12 billion encrypted transactions per day.

In addition to its massive transaction processing capabilities, a mainframe is extremely configurable, supports dynamic reconfigurations and provides hot-swappable hardware components. A mainframe normally runs its own OS, such as IBM's z/OS, but recent models also support Linux, running on bare metal or in virtual machines, considerably increasing the mainframe's capabilities.

Mainframes have a reputation for being resilient, reliable and secure, incorporating some of the most advanced hardware technologies available. Multiple layers of redundancy exist throughout the system to ensure continuous reliability and availability. In addition, admins can cluster mainframes to deliver even greater reliability and availability, especially if the cluster is geographically dispersed, which can help protect against a disaster in any one location.

Mainframes are primarily suited for high-volume, data-intensive workloads with many concurrent, real-time transactions, such as the transactions of banks or other financial institutions. Industries such as utility companies, government agencies and health care systems can also benefit from the power a mainframe computer can offer.

However, a mainframe's high price tag also means that it's not a system for organizations that are simply testing the waters or implementing types of server hardware incrementally. A mainframe might be more cost-effective in the long term depending on the supported workloads, but the initial capital outlay could be too much for many businesses.

Mainframes also require skilled technicians to implement and operate -- a type of admin getting harder to find as much of the attention turns to rack and blade servers. For many organizations, a mainframe comes with a learning curve that might be too steep to take on.

Hyper-converged infrastructure

Organizations in the market for data center servers might also consider hyper-converged infrastructure (HCI), a software-centric system for delivering compute, storage and networking resources in a tightly integrated system. Vendors offer HCI platforms as self-contained appliances, software-only packages or reference architectures.

An HCI platform typically consists of multiple server nodes, a hypervisor for virtualizing resources on each node, and an intelligent software layer that manages and orchestrates resources across the server nodes. In addition, HCI systems usually include built-in data protections, such as mirroring, replication or erasure coding, as well as backup, redundancy and other disaster recovery capabilities.

The compute nodes that make up an HCI platform can be standard, off-the-shelf servers. In addition to the processing and memory resources, each server also includes its own direct-attached storage. Most HCI appliances include at least three nodes, with the ability to add nodes to accommodate growing workloads.

The intelligent software consolidates the resources from each server into a shared resource pool, delivering a high degree of flexibility while also simplifying management. Scaling the system is merely a matter of adding another server node. However, the server nodes must be identical, so adding a node can sometimes mean purchasing resources that are not always necessary in order to boost the compute resources.