KVM

A KVM switch ("keyboard, video and mouse") is a hardware device that allows a user to control multiple computers from one or more keyboard, video monitor and mouse. A KVM (switch) is primarily used to control multiple computers from the same 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. Basically used for remote administration of servers.

KVM switches are 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.

The advantage KVM has over conventional methods of remote administration is that KVM does not depend on any software running on the remote server. KVM allows you to monitor your server right from the its booting up and even interact with the base level BIOS setting. Most KVM over IP devices support the web browser as the user interface so no client software is required.

Many hosting providers provide you with access to a Remote Console. But while having access to your remote server via a Remote Console is great keep in mind that a Remote Console uses an out-of-band management switch to redirect the computers serial console input and output over a secure internet connection to the remote user and this service requires that the server OS is up and running. This is where KVM scores over Remote Console as KVM do not depend on the OS and even offers BIOS level control.

I guess it’s easy to identify the function of the above figures.

EXTRA: Out-of-band management (sometimes called lights-out management or LOM) involves the use of a dedicated management channel for device maintenance. It allows a system administrator to monitor and manage servers and other network equipment by remote control regardless of whether the machine is powered on, or if an operating system is installed or functional.

By contrast, in-band management like VNC and SSH is based on software that must be installed on the remote system being managed and only works after the operating system has been booted. This solution may be cheaper, but it does not allow access to BIOS settings or the reinstallation of the operating system and cannot be used to fix problems that prevent the system from booting.

Both in-band and out-of-band management is usually done through the network connection, but an out-of-band management card can use a physically separated network connector if preferred. A remote management card usually has an at least partially independent power supply, and can power the main machine on and off through the network.