A computer appliance is a specialized computing device with special hardware and/or software built to serve a particular need or function. Computer appliances differ from general-purpose computers such as a desktop computer or server in that they are usually not designed to be modified by the end user. All functionality is 'sealed in' at the factory in some way.
A computer appliance is often, but not always, built with specialized processors called 'application specific integrated chips' (ASICs) or programmable logic controllers (PLCs) that have special optimizations in their design to make them faster and more efficient at a specific task such as processing video, network packet inspection and forwarding, or encryption. Some computer appliances simply have a suite of specialized software that has been integrated inside the computer appliance in such a way as to bring significant capabilities to bear on a common information technology problem, such as security, SPAM and virus blocking or networking.
Computer Appliance Tutorial Topics
- Types of Computer Appliances
- Advantages of Computer Appliances
- Computer Appliance Limitations
- Computer Appliance Architecture
Types of Computer Appliances
Appliances are custom-built to fit a particular market segment, such as home users, small offices, enterprises and communications carriers. Most are designed for small-office and home use, and come with a web browser based management interface used to make user-configurable changes to the device and manage the computer appliance's services. Examples of a computer appliance include the following:
- Storage Appliance
- A storage appliance provides a very large data storage capacity that is
made available to all the computers on the network through shares configured
on the on-board computer used to manage and control the storage unit.
Storage appliances are often designed to support larger numbers of hard
drives and to make that space available over a network or fiber-optic
communications 'fabric'.
- Network Appliance
- Network appliances often have specialized software and/or processors for
routing and forwarding packets and performing security functions running
on a specialized programmable logic controller and application specific
integrated chips. Typically aimed at home and small office use, these
devices combine network switch, routing and firewall functionality in
a single device with a web browser based administrative interface.
- Security Appliance
- Security Appliances often contain specialized software and/or processors to perform packet inspection, encryption or other functions.
Advantages of Computer Appliances
The Computer Appliance Sales Pitch:
- Low-cost
- Easy and quick to install--plug it in and use it immediately
- No specialized knowledge required
- Buy more appliances when you need them
The computing appliance sales pitch is that the computing appliance will be to be easy to use: 'simply plug in and turn on'. The sales pitch continues that no specialized knowledge is required, and that the desired functionality will instantly be available, quickly and easily at a low cost, saving businesses and end users time and effort. The advertising will describe the device as being as easy to use as a kitchen toaster. The reality may be somewhat different.
Computer Appliance Limitations
The Computer Appliance Reality:
- The computer appliance might work as advertised
- Accessing the full functionality of the computer appliance usually requires additional purchases of modules, firmware or licenses.
- The computer appliance may have unadvertised limitations.
- The computer appliance may not fully fit the actual need (see previous point)
- You WILL pay for additional features and upgrades, if upgrading is even possible.
- Can't access the system's internals to tailor the system to fit your needs
- The Solution provided may be proprietary, and incompatible with other products, services or solutions
- Can't update the system to close security vulnerabilities
- May have to remove the device and replace it to upgrade.
- Management overhead--too many devices to keep track of easily, and each appliance has to be configured individually.
While these computing appliances can often be configured, they frequently can't be modified and upgrades can be limited. The vendor has 'sealed in' the configuration and functionality at the factory. If additional functionality is needed, an additional purchase of a 'firmware image' or license key is required, or the device must be removed and replaced with a more powerful (and more expensive) solution. Usually if a computing appliance can be modified, it is usually only the manufacturer that can do so, and often it costs money and sometimes expensive consultants.
It is not uncommon for a software company to offer an appliance version of their product as an 'entry level' product, which later leads to the purchase of the full software product later when the end user finds out that the appliance doesn't quite fit their needs.
Computer Appliance Architecture
Home and SoHo Computer Appliances
Small computer appliances for home or small office use will come 'sealed' at the factory as a single integrated component board inside a small form-factor plastic case. Within the plastic case you will find most of the following components, integrated into a single logic board:
- Flash Memory
- Processor or Application-Specific Integrated Chip(s) (ASICs)
- RAM
- Wireless (WiFI) or wired Ethernet Network port
- USB Port
- Linux-based operating system or micro-kernel
- Virtual Machine or Java Virtual Machine
- Web server with administrative interface
Server Appliances
Enterprise-class computer appliances usually consist of a standard computer or server with one or more specialized software suites installed on top of a customized operating system. Because a standard computer is used, the computer is much the same as any other computer and easily maintained by IT professionals with experience in basic server administration. Because the software resides on an standard computer hard drive, the software may be patched or upgraded by using a built-in vendor-provided update function which downloads the patch or update from the vendor's website over the Internet and applies it automatically to the server.