Server Redundancy

Redundancy, in general, refers to a system’s critical functions’ or components’ duplication, usually as a backup, with an aim to enhance the system’s reliability or for the improvement of the performance of the system. There are four main forms of redundancy, which include hardware, software, time and information. Usually it is hardware redundancy that is referred to, in the context of ensuring redundancy for an infrastructure project. When a duplicate component or device is added in a system, for it to step in during the failure of the primary component or device, then it is understood as hardware redundancy. It is aimed at ensuring that there is no downtime. Now, why is the term “redundancy” used, if the aim is to attain zero downtime? That is because when all the functions or components of a system are working properly, the duplicate component has no role to play and does nothing, which renders it redundant.

Let us understand the concept of redundancy with the example of a hard drive. Usually, hard drives are known to be redundancy’s most common form. In the simplest set up, a primary drive will be regularly copied to a backup drive. In the event that the primary drive fails, the secondary drive is used. In this situation, the data that is lost includes such data that have been produced post the time the files were copied.

Redundancy and Servers

In the context of servers, uptime is extremely important. For this reason server redundancy plays a vital role in this matter. Before proceeding any further, let us understand what a server is, for the benefit of the uninitiated.

Servers

A server can either be any hardware device or software, which accepts and responds to the requests of clients by fulfilling those requests. These requests are made over a network. Clients are the devices that generate the requests, and subsequently receive a server’s responses. A server is meant to provide functionality, which is known as service, to its various clients (programs or devices) by using the client-server model. There are many types of servers, such as database servers, file servers, mail servers, print servers, application servers, game servers, proxy servers, web servers etc. Let us take the example of a web server, and understand the role that a server plays, and let us also touch upon the importance of server redundancy in the context of web servers.

Web Servers

A web server is a type of a server, which is used by web hosting companies for the purpose of providing the service of web hosting. It functions by accepting and then fulfilling the Hypertext Transfer Protocol (HTTP) messages as requests of browsers or mobile applications (clients) for websites’ content, such as videos, images, HTML pages etc.

A web server stores the files of different types of websites, and delivers those files over the Internet, after receiving requests. When the files are delivered to the devices of the users, such as mobile phones, laptops etc. then websites become accessible. Web hosting companies not only provide space on their web servers but also all the technologies and services that make it possible for websites to remain up and running constantly. Terms such as the “Best Website Hosting Company”, the “Best Cloud Hosting Company”, the “Best Windows Hosting Company” etc. are used for the most well-known web hosting service providers. Every web hosting company aims at providing high uptime as their customers’ websites need to be up and running seamlessly to cater to their visitors’ requirements. Since redundancy aims at attaining zero downtime, it becomes very crucial for web servers. If anything goes wrong with the primary web server or it gets a huge volume of traffic, the redundant server takes over, and ensures the continuity of the service of web hosting.

Server Redundancy Explained

The term “server redundancy” is used to refer to the amount as well as the intensity of backup or servers that are redundant in any computing environment. It indicates a computing infrastructure’s capability with regard to making available additional servers. These additional servers can be deployed on runtime for ensuring backup as well as for load balancing. These can also be used when a primary server needs to be halted temporarily for the purpose of carrying out maintenance on it. Server redundancy always ensures that there is a backup server ready and waiting to chip in, if the primary server fails to provide service.

The implementation of server redundancy happens in an enterprise IT infrastructure, as server availability is extremely important in this scenario. A server replica of the primary server is built in order to attain server redundancy. Thus, in order for server redundancy to work, there must be at least two servers, both of which need to contain identical functions and data. One of these is the primary server, which functions live and remains online. The other one is this server’s replica, which is known as the redundant server. This server replica is equipped with the same applications, computing power, storage, operational parameters, etc. as the primary server, which has been replicated.

A redundant server stays offline, and is not used as a live server. But it is always ready to act when the need arises, and can start functioning with Internet/network connectivity and power supply. The redundant server remains inactive as long as there is signal from the primary server, and it is functioning properly. Once that signal changes, the redundant server takes over instantaneously and automatically unless the option of manual switch has been opted for. This option generates an automated alert when anything goes wrong with a primary server, and subsequently a swap to the redundant server could be authorized. When the primary server resumes proper functioning, traffic gets routed to it once again. In this way, server redundancy ensures that the users of the primary servers experience no difference in the quality of the service or any interruption in it.

Types of Redundant Servers

There can be several forms of redundant servers, such as replicated servers or redundant domain, front end, and validation servers or disaster recovery servers, etc. Let us elaborate on each of these.

• Replicated servers- These could be paired with production servers. The changes made to the latter are replicated to the former with the aid of hardware-based or software-based tools. These replicated servers can be used when the production servers fail.

• Redundant domain, front end, and validation servers- These are used for the purpose of load balancing, so that users never lose access to a service.

• Disaster recovery servers- These ensure that backup files get restored quickly, and these restart processing whenever there is the need for it.

Conclusion

Server redundancy aids in ensuring that whenever a primary server experiences downtime, excessive traffic or failure, a redundant server can be implemented and used to replace the primary server or to aid its capabilities by sharing its traffic load. Server redundancy is an efficient solution for maintaining uptime along with being an effective disaster recovery option. Its only downside is that it increases the overall cost. Moreover, these additional servers need to be maintained, and one needs to take into account the cooling as well as the space related requirements.

The goal of server redundancy is to deliver a reliable solution for the servers’ unhindered continuity of service, which is extremely essential for the businesses that rely on these servers. Hence, server redundancy is of paramount importance.

Source: https://www.htshosting.org/knowledge-base/server/127/server-redundancy