If you've ever been inside a server room of a major corporation, a large business, or a university, you know that it can be an intimidating place. The server room is almost always extremely warm, and filled from wall to wall with expensive and space-consuming server racks.

Add to that the fact that these rooms are usually secured like bank vaults, and you have the makings of a truly interesting experience. With virtualization software, a single physical server can run several virtual machines simultaneously. Each of these machines believes it is running on its own dedicated hardware, as if it were separate from all the other machines.

VMWare’s ESX Server (now the ESXi server) is an enterprise level virtualization tool. It utilizes services that manage numerous virtual machines with greater reliability and efficiency than VMware's more basic Server product. The reason for this is because ESX Server runs on "bare-metal."

“Bare metal” means that you install the ESX Server software directly into the computer, without an operating system for it to run on top of. This is illustrated in the diagram below:

The product then divides up the resources from the physical hardware and simulates multiple copies of virtual hardware for the virtual machines to use.

It even has the capability to over-commit memory, meaning the total memory of the virtual machines can safely exceed the actual physical memory of the server. This can make for increased overall memory utilization in your servers.

This is all managed by the service console, which serves as the management software for ESXi Server and its "operating system."

ESX server was the predecessor to the ESXi. This system was managed by the VMkernel, which is based on the Linux kernel. This microkernel saves resources by eliminating the overhead of running an underlying operating system beneath the virtual machines.

The main difference between ESX and ESXi is that the former ran on Linux, and the latter is operating system independent. 

ESXi Server is meant to be used by companies that need to streamline their server hardware as much as possible. It can also be used to perform almost instant deployment of new servers and perform maintenance on existing in-use servers without the need for downtime.

Another interesting use of ESX Server is for disaster recovery. Since ESX Server is hardware independent, the applications (and operating systems) that run on it are instantly portable.

The necessarily uniform nature of the server's hardware and ESX Server's virtual specs make deploying, maintaining, and remotely managing virtual machines extremely easy.

VMWare ESXi does have a free version, albeit with limitations. For an enterprise-level hypervisor, you will likely need to pay to use VMware’s features. You can explore the different licensing levels for ESXi in VMWare’s Vsphere package. 

Now you can consolidate your servers and run more efficiently. Turn that server room from intimidating to just timid. With ESXi Server, you really can't go wrong.

Want to learn more about virtualization? Check out Virtualization in the Real World from Pluralsight.