Опслужувач

„Сервер на мрежа“ води овде. За За Apple производ, видете Apple мрежен сервер.

Сервер е систем (софтвер и соодветен компјутерски хардвер) кој одговара на барањата низ компјутерската мрежа за да обезбеди, или да помогне да се обезбеди, мрежна услуга. Серверите може да работат на специјало наменет компјутер, кој често пати се нарекува "сервер", но многу мрежни компјутери се способни за поставување на сервери. Во многу случаи, компјутерот може да обезбеди неколку услуги и има неколку сервери што работат.

Сервери во центар за податоци. Неколку сервери се монтирани на решетката и поврзани со KVM switch.

Серверите работат во рамките на клиент-сервер архитектура, серверите се компјутерски програми кои работат да им служат на барањата на другите програми, на клиенти. Така, серверот извршува некоја задача во име на клинтот. Клиентите обично се поврзуваат на сервер преку мрежата, но може и да се користи истиот компјутер. Во контекст на Интернет протокол (ИП) вмрежување, серверот е програма со која функционира како приклучок.

Серверите често ги обезбедуваат основните услуги преку мрежа, или на приватните корисници во голема организација или на јавните корисници преку интернет. Типични компјутерски сервери се сервер за база на податоци, сервер за датотеки, меил сервер, сервер за печатење, веб сервер, сервер за игри, апликациски сервер, или некој друг вид на сервер.

Бројни системи го користат овај клиент / сервер мрежен модел вклучувајки веб сајтови и емаил услуги. Алтернативен модел, peer-to-peer мрежа им овозможува на сите компјутери да дејствуваат или како сервер или како клиент колку што е потребно.

Употреба

Терминот сервер се користи доста широко во информатичката технологија. И покрај многуте сервер брендирани производи кои се достапни (како сервер верзии на хардвер, софтвер или оперативни системи), по претпоставка дека еден компјутерски процес споделува ресурси на еден или повеќе клиенти на серверот. Да го прикажеме ова, ќе земеме чест пример на споделување на датотеки. Додека постоењето на датотеки на машината не се класифицира како сервер, механизмот кој ги дели овие датотеки на своите клиенти од страна на оперативниот систем е сервер.

Слично, се смета дека веб сервер апликација (како мултиплатформска "Apache HTTP Сервер"). Овај бев сервер софтвер мозе да биде функционален на секој спремен компјутер. На пример, додека лаптоп или персонален компјутер не е обично познат како сервер, тие во овие ситуации може да ја исполнат улогата на еден, и со тоа да бидат означени како еден. Тоа е, во овај случај, улогата на машината што ја става во категоријата на сервер.

Во хардверска смисла, зборот сервер обично означува компјутерски модели наменети за поставување софтверски апликации поради големата побарувачка на мрежана средина. Во оваа клиент–сервер конфигурација една или повеќе машини, или еден компјутер или компјутер апарат, споделува информации едни со други со едно делување како домаќин за други.

While nearly any personal computer is capable of acting as a network server, a dedicated server will contain features making it more suitable for production environments. These features may include a faster CPU, increased high-performance RAM, and increased storage capacity in the form of a larger or multiple hard drives. Servers also typically have reliability, availability and serviceability (RAS) and fault tolerance features, such as redundancy in power supplies, storage (as in RAID), and network connections.

Servers became common in the early 1990s as businesses increasingly began using personal computers to provide services formerly hosted on larger mainframes or minicomputers. Early file servers housed multiple CD-ROM drives, which were used to host large database applications.^{[се бара извор]}

Between the 1990s and 2000s an increase in the use of dedicated hardware saw the advent of self-contained server appliances. One well-known product is the Google Search Appliance, a unit that combines hardware and software in an out-of-the-box packaging. Also produced were the Cobalt Qube and the RaQ. Simpler examples of such appliances include switches, routers, gateways, and print servers, all of which are available in a near plug-and-play configuration.

Modern operating systems such as Microsoft Windows or Linux distributions seem to be designed with a client–server architecture in mind. These operating systems attempt to abstract hardware, allowing a wide variety of software to work with components of the computer. In a sense, the operating system can be seen as serving hardware to the software, which in all but low-level programming languages must interact using an API.

These operating systems may be able to run programs in the background called either services or daemons. Such programs, such as the aforementioned Apache HTTP Server software, may wait in a sleep state for their necessity to become apparent. Since any software that provides services can be called a server, modern personal computers can be seen as a forest of servers and clients operating in parallel.

The Internet itself is also a forest of servers and clients. Merely requesting a web page from a few kilometers away involves satisfying a stack of protocols that involve many examples of hardware and software servers. The least of these are the routers, modems, domain name servers, and various other servers necessary to provide us the world wide web.

The introduction of Cloud computing allows server storage and other resources to be shared in a pool and provides servers with a higher degree of fault tolerance.

Server hardware

A rack-mountable server. Top cover removed to reveal the internal components.

Hardware requirement for servers vary, depending on the server application. Absolute CPU speed is not quite as critical to a server as it is to a desktop machine ^{[се бара извор]}. Servers' duties to provide service to many users over a network lead to different requirements such as fast network connections and high I/O throughout. Since servers are usually accessed over a network, they may run in headless mode without a monitor or input device. Processes that are not needed for the server's function are not used. Many servers do not have a graphical user interface (GUI) as it is unnecessary and consumes resources that could be allocated elsewhere. Similarly, audio and USB interfaces may be omitted.

Servers often run for long periods without interruption and availability must often be very high, making hardware reliability and durability extremely important. Although servers can be built from commodity computer parts, mission-critical enterprise servers are ideally very fault tolerant and use specialized hardware with low failure rates in order to maximize uptime, for even a short-term failure can cost more than purchasing and installing the system. For example, it may take only a few minutes of down time at a national stock exchange to justify the expense of entirely replacing the system with something more reliable. Servers may incorporate faster, higher-capacity hard drives, larger computer fans or water cooling to help remove heat, and uninterruptible power supplies that ensure the servers continue to function in the event of a power failure. These components offer higher performance and reliability at a correspondingly higher price. Hardware redundancy—installing more than one instance of modules such as power supplies and hard disks arranged so that if one fails another is automatically available—is widely used. ECC memory devices that detect and correct errors are used; non-ECC memory is more likely to cause data corruption.

To increase reliability, most servers use memory with error detection and correction, redundant disks, redundant power supplies and so on. Such components are also frequently hot swappable, allowing technicians to replace them on the running server without shutting it down. To prevent overheating, servers often have more powerful fans. As servers are usually administered by qualified system administrators, their operating systems are also more tuned for stability and performance than for user friendliness and ease of use, Linux taking a noticeably larger percentage than for desktop computers.^{[се бара извор]}

As servers need a stable power supply, good Internet access, increased security and are also noisy, it is usual to store them in dedicated server centers or special rooms. This requires reducing the power consumption, as the extra energy used generates more heat thus causing the temperature in the room to exceed acceptable limits; hence normally, server rooms are equipped with air conditioning devices. Server casings are usually flat and wide (typically measured in "rack units"), adapted to store many devices next to each other in a server rack. Unlike ordinary computers, servers usually can be configured, powered up and down or rebooted remotely, using out-of-band management, typically based on IPMI.

Many servers take quite a long time for the hardware to start up and load the operating system. Servers often do extensive pre-boot memory testing and verification and startup of remote management services. The hard drive controllers then start up banks of drives sequentially, rather than all at once, so as not to overload the power supply with startup surges, and afterwards they initiate RAID system pre-checks for correct operation of redundancy. It is common for a machine to take several minutes to start up, but it may not need restarting for months or years.

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

Server operating systems

Server-oriented operating systems tend to have certain features that make them more suitable for the server environment, such as^{[се бара извор]}

• 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.

Server-oriented operating systems can, in many cases, interact with hardware sensors to detect conditions such as overheating, processor and disk failure, and consequently alert an operator or take remedial measures themselves.

Because servers must supply a restricted range of services to perhaps many users while a desktop computer must carry out a wide range of functions required by its user, the requirements of an operating system for a server are different from those of a desktop machine. While it is possible for an operating system to make a machine both provide services and respond quickly to the requirements of a user, it is common to use different operating systems on servers and desktop machines. Some operating systems are supplied in both server and desktop versions with similar user interface^{[се бара извор]}.

Windows and Mac OS X server operating systems are deployed on a minority of servers, as are other proprietary mainframe operating systems, such as z/OS. The dominant operating systems among servers are UNIX-like open source distributions, such as those based on Linux and FreeBSD. The rise of the microprocessor-based server was facilitated by the development of Unix to run on the x86 microprocessor architecture. The Microsoft Windows family of operating systems also runs on x86 hardware and, since Windows NT, have been available in versions suitable for server use^{[се бара извор]}.

While the role of server and desktop operating systems remains distinct, improvements in the reliability of both hardware and operating systems have blurred the distinction between the two classes. Today, many desktop and server operating systems share similar code bases, differing mostly in configuration. The shift towards web applications and middleware platforms has also lessened the demand for specialist application servers^{[се бара извор]}.

Types of servers

In a general network environment the following types of servers may be found^{[се бара извор]}.

• Application server, a server dedicated to running certain software applications
• Catalog server, a central search point for information across a distributed network
• Communications server, carrier-grade computing platform for communications networks
• Compute server, a server intended for intensive (esp. scientific) computations
• Database server, provides database services to other computer programs or computers
• Fax server, provides fax services for clients
• File server, provides remote access to files
• Game server, a server that video game clients connect to in order to play online together
• Home server, a server for the home
• Mail server, handles transport of and access to email
• Mobile Server, or Server on the Go is an Intel Xeon processor based server class laptop form factor computer.
• Name server or DNS
• Print server, provides printer services
• Proxy server, acts as an intermediary for requests from clients seeking resources from other servers
• Sound server, provides multimedia broadcasting, streaming.
• Stand-alone server, a server on a Windows network that neither belongs to nor governs a Windows domain
• Web server, a server that HTTP clients connect to in order to send commands and receive responses along with data contents

Almost the entire structure of the Internet is based upon a client–server model. High-level root nameservers, DNS, and routers direct the traffic on the internet. There are millions of servers connected to the Internet, running continuously throughout the world.

• World Wide Web
• Domain Name System
• E-mail
• FTP file transfer
• Chat and instant messaging
• Voice communication
• Streaming audio and video
• Online gaming
• Database servers

Virtually every action taken by an ordinary Internet user requires one or more interactions with one or more servers.

There are also technologies that operate on an inter-server level. Other services do not use dedicated servers; for example peer-to-peer file sharing, some implementations of telephony (e.g. Skype), and supplying television programs to several users (e.g. Kontiki, SlingBox)^{[се бара извор]}.

Energy consumption of servers

In |url=http://www.nytimes.com/2011/08/01/technology/data-centers-using-less-power-than-forecast-report-says.html?_r=0 |title=Data Centers Using Less Power Than Forecast, Report Says |date=31 Jul 2011 |publisher=NY Times |accessdate=18 Jan 2013 |first=John |last=Markoff}}</ref>

To put this in context, this is less than the 6 billion cell phones in the world use to recharge their batteries. Moreover, this pales in comparison to double-digit uses like heating and cooling, domestic hot water, ranges, ovens, and clothes dryers, to name a few. Finally, to keep this use in perspective, the Smart2020 report estimates that ICT (Information and Communications Technology) saves more than 5 times its carbon footprint in the rest of the economy by enabling efficiency.

Size classes

Sizes include^{[се бара извор]}:

• rack server
• tower server
• miniature (home) servers
• mini rack servers
• blade server
• Mobile Server

See also

Server definitions

• Home server
• File server
• Print server
• Media server
• Mobile Server