Server (computing)

A computer network diagram of client computers communicating with a server computer via the Internet

The first WWW server is located at CERN with its original sticker that says: "This machine is a server. DO NOT POWER IT DOWN!!"

Server is a computer that provides information to other computers called "clients" on computer network.^[1] This architecture is called the client–server model. Servers can provide various functionalities, often called "services", such as sharing data or resources among multiple clients or performing computations for a client. A single server can serve multiple clients, and a single client can use multiple servers. A client process may run on the same device or may connect over a network to a server on a different device.^[2] Typical servers are database servers, file servers, mail servers, print servers, web servers, game servers, and application servers.^[3]

Client–server systems are usually most frequently implemented by (and often identified with) the request–response model: a client sends a request to the server, which performs some action and sends a response back to the client, typically with a result or acknowledgment. Designating a computer as "server-class hardware" implies that it is specialized for running servers on it. This often implies that it is more powerful and reliable than standard personal computers, but alternatively, large computing clusters may be composed of many relatively simple, replaceable server components.

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Hardware

Hardware requirement for servers vary widely, depending on the server's purpose and its software. Servers often are more powerful and expensive than the clients that connect to them.

The name server is used both for the hardware and software pieces. For the hardware servers, it is usually limited to mean the high-end machines although software servers can run on a variety of hardwares.

Since servers are usually accessed over a network, many run unattended without a computer monitor or input device, audio hardware and USB interfaces. Many servers do not have a graphical user interface (GUI). They are configured and managed remotely. Remote management can be conducted via various methods including Microsoft Management Console (MMC), PowerShell, SSH and browser-based out-of-band management systems such as Dell's iDRAC or HP's iLo.

Large servers

Large traditional single servers would need to be run for long periods without interruption. Availability would have to be very high, making hardware reliability and durability extremely important. Mission-critical enterprise servers would be very fault tolerant and use specialized hardware with low failure rates in order to maximize uptime. Uninterruptible power supplies might be incorporated to guard against power failure. Servers typically include hardware redundancy such as dual power supplies, RAID disk systems, and ECC memory,^[4] along with extensive pre-boot memory testing and verification. Critical components might be hot swappable, allowing technicians to replace them on the running server without shutting it down, and to guard against overheating, servers might have more powerful fans or use water cooling. They will often be able to be configured, powered up and down, or rebooted remotely, using out-of-band management, typically based on IPMI. Server casings are usually flat and wide, and designed to be rack-mounted, either on 19-inch racks or on Open Racks.

These types of servers are often housed in dedicated data centers. These will normally have very stable power and Internet and increased security. Noise is also less of a concern, but power consumption and heat output can be a serious issue. Server rooms are equipped with air conditioning devices.

A server rack seen from the rear
Wikimedia Foundation servers as seen from the front
Wikimedia Foundation servers as seen from the rear
Wikimedia Foundation servers as seen from the rear

Clusters

A server farm or server cluster is a collection of computer servers maintained by an organization to supply server functionality far beyond the capability of a single device. Modern data centers are now often built of very large clusters of much simpler servers,^[5] and there is a collaborative effort, Open Compute Project around this concept.

Appliances

A class of small specialist servers called network appliances are generally at the low end of the scale, often being smaller than common desktop computers.

Mobile

A mobile server has a portable form factor, e.g. a laptop.^[6] In contrast to large data centers or rack servers, the mobile server is designed for on-the-road or ad hoc deployment into emergency, disaster or temporary environments where traditional servers are not feasible due to their power requirements, size, and deployment time.^[7] The main beneficiaries of so-called "server on the go" technology include network managers, software or database developers, training centers, military personnel, law enforcement, forensics, emergency relief groups, and service organizations.^[8] To facilitate portability, features such as the keyboard, display, battery (uninterruptible power supply, to provide power redundancy in case of failure), and mouse are all integrated into the chassis.

Operating systems

On the Internet, the dominant operating systems among servers are UNIX-like open-source distributions, such as those based on Linux and FreeBSD,^[9] with Windows Server also having a significant share. Proprietary operating systems such as z/OS and macOS Server are also deployed, but in much smaller numbers. Servers that run Linux are commonly used as Webservers or Databanks. Windows Servers are used for Networks that are made out of Windows Clients.

Specialist server-oriented operating systems have traditionally had features such as:

GUI not available or optional
Ability to reconfigure and update both hardware and software to some extent without restart
Advanced backup facilities to permit regular and frequent online backups of critical data,
Transparent data transfer between different volumes or devices
Flexible and advanced networking capabilities
Automation capabilities such as daemons in UNIX and services in Windows
Tight system security, with advanced user, resource, data, and memory protection.
Advanced detection and alerting on conditions such as overheating, processor and disk failure.^[10]

In practice, today many desktop and server operating systems share similar code bases, differing mostly in configuration.

Energy consumption

In 2010, data centers (servers, cooling, and other electrical infrastructure) were responsible for 1.1-1.5% of electrical energy consumption worldwide and 1.7-2.2% in the United States.^[11]^{[needs update]} One estimate is that total energy consumption for information and communications technology saves more than 5 times its carbon footprint^[12] in the rest of the economy by increasing efficiency.

Global energy consumption is increasing due to the increasing demand of data and bandwidth. Natural Resources Defense Council (NRDC) states that data centers used 91 billion kilowatt hours (kWh) electrical energy in 2013 which accounts to 3% of global electricity usage.^{[needs update]}

Environmental groups have placed focus on the carbon emissions of data centers as it accounts to 200 million metric tons of carbon dioxide in a year.

Notes

References

^ "1.1.2.2 Clients and Servers". Cisco Networking Academy. Retrieved 2024-04-07. Servers are hosts that have software installed that enable them to provide information...Clients are computer hosts that have software installed that enable them to request and display the information obtained from the server.
^ Windows Server Administration Fundamentals. Microsoft Official Academic Course. Hoboken, NJ: John Wiley & Sons. 2011. pp. 2–3. ISBN 978-0-470-90182-3.
^ Comer, Douglas E.; Stevens, David L (1993). Vol III: Client-Server Programming and Applications. Internetworking with TCP/IP. West Lafayette, IN: Prentice Hall. pp. 11d. ISBN 978-0-13-474222-9.
^ Li, Huang, Shen, Chu (2010). ""A Realistic Evaluation of Memory Hardware Errors and Software System Susceptibility". Usenix Annual Tech Conference 2010" (PDF). Archived (PDF) from the original on 2022-10-09. Retrieved 2017-01-30.{{cite web}}: CS1 maint: multiple names: authors list (link)
^ "Google uncloaks once-secret server". CNET. CBS Interactive. Retrieved 2017-01-30.
^ "Mobile Server, Power to go, EUROCOM Panther 5SE". Archived from the original on 2013-03-17.
^ "Mobile Server Notebook". 27 January 2022.
^ "Server-caliber Computer Doubles as a Mobile Workstation". Archived from the original on 2016-03-03. Retrieved 2020-02-08.
^ "Usage statistics and market share of Linux for websites". Retrieved 18 Jan 2013.
^ "Server Oriented Operating System". Retrieved 2010-05-25.
^ Markoff, John (31 Jul 2011). "Data Centers Using Less Power Than Forecast, Report Says". NY Times. Retrieved 18 Jan 2013.
^ "SMART 2020: Enabling the low carbon economy in the information age" (PDF). The Climate Group. 6 Oct 2008. Archived from the original (PDF) on 22 November 2010. Retrieved 18 Jan 2013.