Computer appliance
Encyclopedia
A computer appliance is generally a separate and discrete hardware device with integrated software (firmware
), specifically designed to provide a specific computing resource. These devices became known as "appliances" because of their similarity to home appliance
s, which are generally "closed and sealed" – not serviceable by the owner. The hardware and software are pre-integrated and pre-configured before delivery to customer, to provide a "turn-key" solution to a particular problem. Unlike general purpose computer
s, appliances are generally not designed to allow the customers to change the software (including the underlying operating system
), or to flexibly reconfigure the hardware.
, which uses the hardware resources of the computer (primarily memory, disk storage, processing power, and networking bandwidth) to meet the computing needs of the user. The main issue with the traditional model is related to complexity. It is complex to integrate the operating system and applications with a hardware platform, and complex to support it afterwards.
By tightly constraining the variations of the hardware and software, the appliance becomes easily deployable, and can be used without nearly as wide (or deep) IT knowledge. As importantly, when problems and errors appear, the supporting staff very rarely needs to explore them deeply and to understand the matter thoroughly. The staff needs merely training on the appliance management software to be able to resolve most of problems.
In all forms of the computer appliance model, customers benefit from easy operations. The appliance has exactly one combination of hardware and operating system and application software, which has been pre-installed at the factory. This prevents customers from needing to perform complex integration work, and dramatically simplifies troubleshooting. In fact, this "turnkey operation" characteristic is the driving benefit that customers seek when purchasing appliances.
To be considered an appliance, the (hardware) device needs to be integrated with software, and both are supplied as a package. This distinguishes appliances from "home grown" solutions, or solutions requiring complex implementations (by integrators or VARs).
The appliance approach helps to decouple the various systems and applications, for example in the data center. Once a resource is decoupled, in theory it can be also centralized to become shared among many systems, centrally managed and optimized, all without requiring changes to any other system.
Types of automation appliances:
adopted by computer appliance vendors, a few of which are shown below. Since the whole concept of an appliance rests on keeping such implementation details away from the end user, it is difficult to match these patterns to specific appliances, particularly since they can and do change without affecting external capabilities or performance.
Sometimes, these techniques are mixed. For example, a VPN
appliance might contain a limited access software firewall running on Linux, with an encryption ASIC to speed up VPN access.
Some computer appliances use solid state storage, while others use a hard drive to load an operating system. Again, the two methods might be mixed—an ASIC print server might allow an optional hard drive for job queueing, or a Linux-based device may encode Linux in firmware
, so that a hard drive is not needed to load the operating system.
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...
), specifically designed to provide a specific computing resource. These devices became known as "appliances" because of their similarity to home appliance
Home appliance
Home appliances are electrical/mechanical machines which accomplish some household functions, such as cooking or cleaning. Home appliances can be classified into:*Major appliances, or White goods*Small appliances, or Brown goods...
s, which are generally "closed and sealed" – not serviceable by the owner. The hardware and software are pre-integrated and pre-configured before delivery to customer, to provide a "turn-key" solution to a particular problem. Unlike general purpose computer
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s, appliances are generally not designed to allow the customers to change the software (including the underlying operating system
Operating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
), or to flexibly reconfigure the hardware.
Overview
Traditionally, software applications run on top of a general-purpose operating systemOperating system
An operating system is a set of programs that manage computer hardware resources and provide common services for application software. The operating system is the most important type of system software in a computer system...
, which uses the hardware resources of the computer (primarily memory, disk storage, processing power, and networking bandwidth) to meet the computing needs of the user. The main issue with the traditional model is related to complexity. It is complex to integrate the operating system and applications with a hardware platform, and complex to support it afterwards.
By tightly constraining the variations of the hardware and software, the appliance becomes easily deployable, and can be used without nearly as wide (or deep) IT knowledge. As importantly, when problems and errors appear, the supporting staff very rarely needs to explore them deeply and to understand the matter thoroughly. The staff needs merely training on the appliance management software to be able to resolve most of problems.
In all forms of the computer appliance model, customers benefit from easy operations. The appliance has exactly one combination of hardware and operating system and application software, which has been pre-installed at the factory. This prevents customers from needing to perform complex integration work, and dramatically simplifies troubleshooting. In fact, this "turnkey operation" characteristic is the driving benefit that customers seek when purchasing appliances.
To be considered an appliance, the (hardware) device needs to be integrated with software, and both are supplied as a package. This distinguishes appliances from "home grown" solutions, or solutions requiring complex implementations (by integrators or VARs).
The appliance approach helps to decouple the various systems and applications, for example in the data center. Once a resource is decoupled, in theory it can be also centralized to become shared among many systems, centrally managed and optimized, all without requiring changes to any other system.
Tradeoffs of the computer appliance approach
The major downside of deploying a computer appliance is that since they are designed to supply a specific resource, they most often include a customized operating system running over specialized hardware, neither of which are likely to be compatible with the other systems previously deployed. Customers lose flexibility.Types of appliances
The variety of computer appliances reflects the wide range of computing resources they provide to applications. Some examples:- Storage appliances provide massive amounts of storage and additional higher level functionality (ex: Disk mirroringDisk mirroringIn data storage, disk mirroring or RAID1 is the replication of logical disk volumes onto separate physical hard disks in real time to ensure continuous availability...
and Data stripingData stripingIn computer data storage, data striping is the technique of segmenting logically sequential data, such as a file, in a way that accesses of sequential segments are made to different physical storage devices. Striping is useful when a processing device requests access to data more quickly than a...
) for multiple attached systems using the transparent local Storage area networks paradigm. - Network appliances are general purpose routers which provide firewallFirewall (computing)A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass....
protection, Transport Layer SecurityTransport Layer SecurityTransport Layer Security and its predecessor, Secure Sockets Layer , are cryptographic protocols that provide communication security over the Internet...
(TLS), messaging, access to specialized networking protocols (like the ebXMLEbXMLElectronic Business using eXtensible Markup Language, commonly known as e-business XML, or ebXML as it is typically referred to, is a family of XML based standards sponsored by OASIS and UN/CEFACT whose mission is to provide an open, XML-based infrastructure that enables the global use of...
Message Service) and bandwidth multiplexingMultiplexingThe multiplexed signal is transmitted over a communication channel, which may be a physical transmission medium. The multiplexing divides the capacity of the low-level communication channel into several higher-level logical channels, one for each message signal or data stream to be transferred...
for the multiple systems they front-end. - Anti-spam appliancesAnti-spam appliancesAnti-spam appliances are hardware devices integrated with on-board software that implement anti-spam techniques and/or anti-spam for instant messaging and are deployed at the gateway or in front of the mail server. They are normally driven by an operating system optimized for spam filtering...
for e-mail spamE-mail spamEmail spam, also known as junk email or unsolicited bulk email , is a subset of spam that involves nearly identical messages sent to numerous recipients by email. Definitions of spam usually include the aspects that email is unsolicited and sent in bulk. One subset of UBE is UCE... - Virtual machine appliances consist of a "hypervisor style" embedded operating system running on appliance hardware. The hypervisor layer is matched to the hardware of the appliance, and cannot be varied by the customer, but the customer may load other operating systems and applications onto the appliance in the form of virtual machines.
Consumer appliances
Aside from its deployment within data centers, many computer appliances are directly used by the general public. These include:- Digital video recorderDigital video recorderA digital video recorder , sometimes referred to by the merchandising term personal video recorder , is a consumer electronics device or application software that records video in a digital format to a disk drive, USB flash drive, SD memory card or other local or networked mass storage device...
- Residential gatewayResidential gatewayA residential gateway is a home networking device, used as a gateway to connect devices in the home to the Internet or other WAN.It is an umbrella term, used to cover multi-function networking computer appliances used in homes, which may combine a DSL or cable modem, a firewall, a consumer-grade...
- Network-attached storageNetwork-attached storageNetwork-attached storage is file-level computer data storage connected to a computer network providing data access to heterogeneous clients. NAS not only operates as a file server, but is specialized for this task either by its hardware, software, or configuration of those elements...
(NAS) - Video game consoleVideo game consoleA video game console is an interactive entertainment computer or customized computer system that produces a video display signal which can be used with a display device to display a video game...
Appliances in industrial automation
The world of industrial automation has been rich in appliances. These appliances have been hardened to withstand temperature and vibration extremes. These appliances are also highly configurable, enabling customization to meet a wide variety of applications. The key benefits of an appliance in automation are:- Reduced downtimeDowntimeThe term downtime is used to refer to periods when a system is unavailable.Downtime or outage duration refers to a period of time that a system fails to provide or perform its primary function...
- a failed appliance is typically replaced with a COTS "commercial off-the-shelfCommercial off-the-shelfIn the United States, Commercially available Off-The-Shelf is a Federal Acquisition Regulation term defining a nondevelopmental item of supply that is both commercial and sold in substantial quantities in the commercial marketplace, and that can be procured or utilized under government contract...
" replacement and its task is quickly and easily reloaded from a backup. - Highly scalable - appliances are typically targeted solutions for an area of a plant or process. As the requirements change, scalability is achieved through the installation of another appliance. Automation concepts are easily replicated throughout the enterprise by standardizing on appliances to perform the needed tasks, as opposed to the development of custom automation schemes for each task.
- Low TCO (total cost of ownershipTotal cost of ownershipTotal cost of ownership is a financial estimate whose purpose is to help consumers and enterprise managers determine direct and indirect costs of a product or system...
) - appliances are developed, tested and supported by automation product vendors and undergo a much broader level of quality testing than custom designed automation solutions. The use of appliances in automation reduce the level of testing needed in each individual application. - Reduced design time - appliances perform specific functions and although they are highly configurable, they are typically self documenting. This enables appliance based solutions to be transferred from engineer to engineer with minimal need for training and documentation.
Types of automation appliances:
- PLC (programmable logic controller) - Programmable logic controllerProgrammable logic controllerA programmable logic controller or programmable controller is a digital computer used for automation of electromechanical processes, such as control of machinery on factory assembly lines, amusement rides, or light fixtures. PLCs are used in many industries and machines...
s are appliances that are typically used for discrete control and offer a wide range of Input and Output options. They are configured through standardized programming languages such as IEC-1131. - SLC (single loop controller) - Single loop controllersPID controllerA proportional–integral–derivative controller is a generic control loop feedback mechanism widely used in industrial control systems – a PID is the most commonly used feedback controller. A PID controller calculates an "error" value as the difference between a measured process variable and a...
are appliances that monitor an input variable and affect change on a control output (manipulated variable) to hold the input variable to a setpoint. - PAC (programmable automation controller) - Programmable automation controllerProgrammable automation controllerA programmable automation controller ' is a compact controller that combines the features and capabilities of a PC-based control system with that of a typical programmable logic controller . PACs are most often used in industrial settings for process control, data acquisition, remote equipment...
s are appliances that embody properties of both PLCs and SLCs enabling the integration of both analog and discrete control. - Universal gateway - A universal gatewayUniversal gatewayA universal gateway is a device that transacts data between two or more data sources using communication protocols specific to each. Sometimes called a universal protocol gateway, this class of product is designed as a computer appliance, and is used to connect data from one automation system to...
appliance has the ability to communicate with a variety of devices through their respective communication protocols, and will affect data transactions between them. This in increasingly important as manufacturing strives to improve agility, quality, production rates, production costs and reduce downtime through enhanced M2M (machine to machineMachine to MachineMachine-to-Machine refers to technologies that allow both wireless and wired systems to communicate with other devices of the same ability...
) communications. - EATMs (enterprise appliance transaction modules) - Enterprise appliance transaction modules are appliances that affect data transactions from plant floor automation systems to enterprise business systems. They communicate to plant floor equipment through various vendor automation protocols, and communicate to business systems through database communication protocols such as JMS (Java Message ServiceJava Message ServiceThe Java Message Service API is a Java Message Oriented Middleware API for sending messages between two or more clients. JMS is a part of the Java Platform, Enterprise Edition, and is defined by a specification developed under the Java Community Process as JSR 914...
) and SQL (Structured Query LanguageSQLSQL is a programming language designed for managing data in relational database management systems ....
).
Internal structure
There are several design patternsDesign Patterns
Design Patterns: Elements of Reusable Object-Oriented Software is a software engineering book describing recurring solutions to common problems in software design. The book's authors are Erich Gamma, Richard Helm, Ralph Johnson and John Vlissides with a foreword by Grady Booch. The authors are...
adopted by computer appliance vendors, a few of which are shown below. Since the whole concept of an appliance rests on keeping such implementation details away from the end user, it is difficult to match these patterns to specific appliances, particularly since they can and do change without affecting external capabilities or performance.
- Special chip - the vendor builds an ASICApplication-specific integrated circuitAn application-specific integrated circuit is an integrated circuit customized for a particular use, rather than intended for general-purpose use. For example, a chip designed solely to run a cell phone is an ASIC...
, without any separate "software" or operating system. The appliance has a limited interface, usually terminal console or web-based, to allow some basic configuration by the IT staff. The manufacturer often provides some way of accessing deeper configuration mechanisms. Azul SystemsAzul SystemsAzul Systems, Inc., a privately held company, develops runtime platforms for executing Java-based applications. Founded in March 2002, Azul Systems is headquartered in Sunnyvale, California, with offices in Slough, United Kingdom; Tokyo, Japan and Bangalore, India.- Products :Azul produces Zing, a...
' Vega 3 Java Compute Appliance is an example; special hardware modifications to the chip enable Java application scaling. - Special software kernel - the vendor uses or creates a general-purpose computer, and designs a new operating system that integrates the application into the operating system. Cisco'sCisco SystemsCisco Systems, Inc. is an American multinational corporation headquartered in San Jose, California, United States, that designs and sells consumer electronics, networking, voice, and communications technology and services. Cisco has more than 70,000 employees and annual revenue of US$...
IOSCisco IOSCisco IOS is the software used on the vast majority of Cisco Systems routers and current Cisco network switches...
is an example; the Unix-like operating system has firewall functions and network/firewall configuration commands built into it. Sometimes, the device is also sealed, so the consumer has no access to reinstall the operating system or replace it with another operating system. The consumer may also be restricted to a small group of configuration commands, while the more detailed and lower level functions of the operating system are only available to the vendor. The more this "locked down" approach is carried out, the closer this type of device comes to appearing like an ASIC device. - Specialized application - off-the-shelf computers and operating systems are used, but the user interface and "box" are designed so the user cannot access anything on the computer, except for the application interface that the vendor has created. Since the underlying computing architecture is locked down and essentially invisible, it becomes difficult to discern that the device really functions on top of general purpose hardware and operating systems. Linux, and BSDBerkeley Software DistributionBerkeley Software Distribution is a Unix operating system derivative developed and distributed by the Computer Systems Research Group of the University of California, Berkeley, from 1977 to 1995...
to a lesser degree, has become the operating system of choice for this type of appliance. Recently the term software applianceSoftware applianceA software appliance is a software application that might be combined with just enough operating system for it to run optimally on industry standard hardware or in a virtual machine....
has also been used to describe such a pre-packaged, black-box combination. - Virtual appliance - here the hardware itself has disappeared entirely and become a so-called virtual applianceVirtual applianceA virtual appliance is a virtual machine image designed to run on a virtualization platform ....
(also known as a virtual software appliance) using any one of a number of virtual machineVirtual machineA virtual machine is a "completely isolated guest operating system installation within a normal host operating system". Modern virtual machines are implemented with either software emulation or hardware virtualization or both together.-VM Definitions:A virtual machine is a software...
technologies. Within this virtual machine is essentially the same stack of software plus the operating system as in the "specialized application" alternative.
Sometimes, these techniques are mixed. For example, a VPN
Virtual private network
A virtual private network is a network that uses primarily public telecommunication infrastructure, such as the Internet, to provide remote offices or traveling users access to a central organizational network....
appliance might contain a limited access software firewall running on Linux, with an encryption ASIC to speed up VPN access.
Some computer appliances use solid state storage, while others use a hard drive to load an operating system. Again, the two methods might be mixed—an ASIC print server might allow an optional hard drive for job queueing, or a Linux-based device may encode Linux in firmware
Firmware
In electronic systems and computing, firmware is a term often used to denote the fixed, usually rather small, programs and/or data structures that internally control various electronic devices...
, so that a hard drive is not needed to load the operating system.
See also
- Automotive navigation systemAutomotive navigation systemAn automotive navigation system is a satellite navigation system designed for use in automobiles. It typically uses a GPS navigation device to acquire position data to locate the user on a road in the unit's map database. Using the road database, the unit can give directions to other locations...
- Green computingGreen computingGreen computing or green IT, refers to environmentally sustainable computing or IT. In the article Harnessing Green IT: Principles and Practices, San Murugesan defines the field of green computing as "the study and practice of designing, manufacturing, using, and disposing of computers, servers,...
- Hardware accelerationHardware accelerationIn computing, Hardware acceleration is the use of computer hardware to perform some function faster than is possible in software running on the general-purpose CPU...
- Information applianceInformation applianceIn general terms, an information appliance or information device is any machine or device that is usable for the purposes of computing, telecommunicating, reproducing, and presenting encoded information in myriad forms and applications....
- Linux devicesLinux devicesLinux-based devices or Linux devices are computer appliances that are powered by the Linux kernel and possibly other parts of the Linux operating system. They are often minimalistic and purpose-built, thus may be environmentally friendly and create less electronic waste per unit.Linux devices are...
- Personal digital assistantPersonal digital assistantA personal digital assistant , also known as a palmtop computer, or personal data assistant, is a mobile device that functions as a personal information manager. Current PDAs often have the ability to connect to the Internet...
(PDA) - Plug computerPlug computerA plug computer is a small form factor server for use in the home or office. Compared to their PC-based counterparts, plug computers are lower cost, consume less power, often do not have a video card, and are intended to be powered up at all times...
- Server applianceServer applianceA server appliance is a computer appliance that works as a server. It is designed so that the end-user does not need to understand the details of the operating system or the commands associated with it. Server appliances have their hardware and software preconfigured by the manufacturer. The...
- SmartphoneSmartphoneA smartphone is a high-end mobile phone built on a mobile computing platform, with more advanced computing ability and connectivity than a contemporary feature phone. The first smartphones were devices that mainly combined the functions of a personal digital assistant and a mobile phone or camera...
- Software applianceSoftware applianceA software appliance is a software application that might be combined with just enough operating system for it to run optimally on industry standard hardware or in a virtual machine....