In the context of a KVM switch the KVM is an acronym for Keyboard, Video/Visual Display Unit and Mouse. The idea behind the creation of the KVM switch is that in certain computing environments having a dedicated keyboard, monitor and mouse for every computer in the system is wasteful particularly when computers such as rack mount servers by their very nature demand very little direct user input.
In most instances; once configured and fully functional, an operator may not be required to interact directly with the server for considerable periods of time. Thus the energy and space saved by not dedicating a keyboard, monitor and mouse for every computer can; particularly in the case of large data centers, be very considerable indeed. The capital outlay for what would otherwise have been seriously underutilized hardware assets can therefore be put to other uses such as purchasing more servers or hard drives.
For standard rack mount server systems it is common for one keyboard, monitor and mouse to be used in combination with an appropriately configured KVM switch(s) to control all member devices of that rack and sometimes adjacent racks as well. It is important to note that enterprise data centers are not the only instances where KVM switches are regularly used.
Being a hardware device of varying connectivity specifications smaller KVM switches have found regular use in the controlling of multiple computing devices through a single user/operator location for device access and interaction via a common set of I/O devices (the keyboard, monitor and pointing device) in small business and home applications.
For instance a very common example of home use is to enable a user the use of the full-size keyboard, mouse and monitor of the home PC to interact with a portable device such as a laptop, tablet PC or PDA. Very popular for overcoming small keyboard issues when big fingers really require bigger keys for maximum efficiency of work output. Controlling a home media center is another popular home application in which small KVM switches are regularly deployed.
It must also be noted that KVM switches also play a role in situations where it is desirable to have varying degrees of interactive input with a computing device from multiple locations of relatively close proximity. The publicly accessible shop kiosk with restricted user interface and an administrative interface located in a more secure position (behind the shop counter or in the next room) is a classic example that demonstrates but one common valid use of this KVM switch in reverse type functionality. Home theatres are another situation that this type of reverse KVM switch functionality is currently being rapidly adopted since most current versions of KVM switches also have the ability to share USB devices and speakers with multiple computers.
Note also that while multiple computers are connected to the KVM switch it is typical for only a small number of them to be under direct operator control at any given moment in time. Part of the reason for this is the impracticality of an operator being able to successfully juggle their way through controlling 20 machine interfaces concurrently for extended periods of time. Network access is by far a better mechanism in these cases.
Implementation, Configuration and Operation
In the majority of instances KVM switches are deployed by the user connecting a keyboard, monitor and mouse to the KVM device using the standard default cables and connectors supplied by their manufacturer. After which specialty cables (typically USB and VGA D-sub) are used to connect the KVM device to the desired computers.
Device control switching from one computer to the next is performed by the user through the use of switches, toggles or buttons located on the KVM device itself. The KVM device automatically manages signal switching between computers, keyboard, monitor and mouse depending upon the current user set computer selection.
Today most KVM devices (except for the very budget versions) also provide keyboard hotkey switching capabilities. This may be as simple is hotkey scrolling from one attached computer to the next or in the more sophisticated units the capacity to “go direct” is built into the KVM device. This saves considerable time since it is rare for the machines in a server rack requiring attention to be conveniently connected adjacently.
For example; it is more likely that devices 3, 8, 14 & 25 in a rack will require attention rather than devices 3, 4, 5, 6 & 7 or some other convenient sequence. In addition it is also likely that the order in which the devices need to be attended to will not be arranged in either ascending or descending numerological sequence but will be defined by other parameters such as the functional uses of the device in question. You may need to configure the authentication server and web servers more regularly than your backup servers.
KVM device differ considerably in terms of the number of computing devices that can be simultaneously connected to or through them. Anywhere from two up to 512 computer connectivity configurations are available. Enterprise class KVM devices also permit daisy-chaining of KVM switches thereby exponentially increasing the total possible number of devices that can be accessed via the one operator keyboard/monitor/mouse combination.
Current Enterprise KVM Switch Uses
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.
Used in conjunction with networking hardware; such as routers and switches, an operator can use an “administrative” machine which can be used to control large arrays of servers thereby reducing even further the need for dedicated keyboards, monitors and mouse. The KVM switch is used to switch between machines interconnected on different LANS, VLANs and router interfaces.