KVM Switch
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A KVM switch (with KVM being an initialism for Keyboard, Video, Mouse) is a hardware device that allows a user to control multiple computers from a single keyboard, video monitor and mouse. Although multiple computers are connected to the KVM, typically a smaller number of computers can be controlled at any given time. This is referred to as the 'Blocking Factor'. Modern devices have also added the ability to share USB devices and speakers with multiple computers.
A user connects a monitor, keyboard, and mouse to the KVM device, then uses special cables to connect the KVM device to the computers. Control is switched from one computer to another by the use of buttons on the KVM device, with the KVM passing the signals between the computers and the keyboard, mouse and monitor depending on which computer is currently selected. Most devices also allow control to be switched through keyboard commands (such as hitting a certain key, often Scroll Lock, rapidly two or three times). Some KVM devices also send signals to the computers that are not currently selected to ensure that they do not think that the keyboard, mouse and monitor are dis-connected.
Devices differ in the number of computers that can be connected, with anywhere from two up to 64 computers possible. Enterprise-grade devices can also be daisy-chained to allow even greater numbers of computers to be controlled from a single set of a keyboard, video and mouse.
A KVM switch is useful where there are multiple computers, but no need for a dedicated keyboard, monitor and mouse for each one. They are frequently used in data centers where multiple servers are placed in a single rack with a single keyboard, monitor and mouse. A KVM switch then allows data center personnel to connect to any server in the rack.
There are software alternatives to a hardware KVM switch such as Synergy, Virtual Network Computing (VNC), teleport or the non-free MaxiVista, Multiplicity and PC Anywhere, which do the switching in software and forward input over standard network connections. This has the advantage of reducing the number of wires needed, and the screen-edge switching it provides makes it easier to forget that you are using two computers. However, there are some disadvantages. Software alternatives typically require additional software to be pre-loaded onto each one of the target servers or computers to allow clients to remotely attach to. They also can not be used when the host Operating System is not installed yet or has not started: operating system installations are thus not possible nor is access to a computer's BIOS or other built-in configuration areas. Finally, the software alternatives can be difficult or impossible to access if the computer is very busy or stopped responding to network connections.
Remote KVM devices (KVM/ip)
Remote KVM devices are also available that allow multiple computers to be controlled remotely across a wide area network, local area network or telephone-line using the TCP/IP protocols and a web browser or specially designed viewer software. A big advantage of this viewer software over a browser based application is the belief that ActiveX or Java security issues are eliminated creating a safer KVM over IP access method, although this may not always be true, given that the viewer software provided by many manufacturers is also reliant on Active X or Java. In addition, some manufacturers charge additional licensing fees for this software. In comparison to conventional methods of remote administration (for example Virtual Network Computing or Terminal Services), a KVM switch has the advantage that it doesn't depend on a software component running on the remote computer, thus allowing remote editing of BIOS settings and monitoring of the entire booting process. Modern KVM over IP gateways or switches use 128-bit data encryption securing the KVM configuration over a WAN or LAN.
Related Technology
- Console server — For managing a command-line driven system through a remote terminal.
KVM Vendors
- [42U KVM] - An Independent KVM Product and Datacenter Specialist
- [Adder Technology] - A leading European developer of KVM switches, extenders and kvm via IP technology based in the United Kingdom
- Aten Technology, Inc. - A leading international manufacturer of KVM switches, splitters, and extenders
- Avocent Corporation - A KVM manufacturer based in Alabama, USA
- [Belkin] - A leading developer of KVM switches for home and business users
- [Black Box] - Manufacturer of a wide range of single and multi user KVM Switches (ServSwitch).
- [ConnectPRO, Inc.] - A manufacturer of analog and remote KVM switches and Video switches and splitters
- Cyclades Corporation - A KVM manufacturer based in California, USA
- [DAXTEN KVM] - KVM manufacturer and distributor for name brand KVM switches, extenders, splitters and rack mount monitors. Offices worldwide.
- [Eclipse International Marketing Inc.] - Canadian KVM distributor of all major brands of KVM products
- [KVM Switches Online] - Online reseller of major KVM vendors.
- [Kvm Depot] - Online US source for all major brands of KVM products.
- [Linksys] - Linksys offers some KVM switches on our market
- [Minicom Advanced Systems] - A leading manufacturer of innovative KVM switches
- [Opengear] - A secure KVM and console server manufacturer focused on leveraging and providing open source and non-proprietary solutions
- [PacificCable.com] - Sells KVM Switches as well as computer, video, audio and home theater cables.
- Raritan Computer - A KVM manufacturer based in New Jersey, USA
- [Zantech KVM Australia] - An Independent KVM Product Specialist based in Australia
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