VMWare ESX Server for Not Yet Techies

VMWare ESX Server is a high end, enterprise tool for the virtualization of Intel servers and operating systems, particular where an organization is using a lot of host computers.

That is, with VMWare ESX Server a large organization can set one computer (server) so that it does the work for many other servers, which may be required for different types of applications. Therefore, you get the work of many different servers with one machine.

With just one hard drive, VMWare ESX Server hosts multiple, logical or virtual server, including individual BIOS. It handles the partitioning and migrating.

The software of VMWare ESX Server imitates hard ware so that the various server software programs running on it think that they are interacting with actual hardware, but in reality are simply interacting with software imitations.

Since it's only software, it doesn't know the difference. Because software can't sense the physical hardware it's running on -- it just interacts with operating system representations of it.

This is known as a virtual machine, and is not a new idea. The programming language Java is founded on this.

So one VMWare ESX Server could have 5 separate programs running which all think they're interacting with the same port, but none of them are.

There are other software programs on the market which do the same thing on a smaller scale (and some are also produced by the VMWare company), but they tie up resources because they run on top of the hardware's actual operating system.

For example software programmers can set up such software on their own PC so that they can test how a program runs in Linux (for example) even though their PC is Windows.

So there're 4 levels:

1. Host machine (the actual hardware)

2. Virtualization software

3. Virtual machine (this is the representation of hardware created by the virtualization software to "fool" the next layer.

4. Guest operating system

So you can have as many guest operating systems as you want, within the limits of the hardware's capacity.

So VMWare GSX Server is a step beyond the company's other products, VMWare Workstation and VMWare GSX.

1. ESX Server kernel -- VMkernel

2. Console Operating System -- COS or VMnix (a customized kernel from the Red Hat 7.2 Linux distribution)

The virtual hardware that VMWare ESX represents itself as is the Intel 440 BX chipset.

It includes such hardware as:

1. Processor

2. Hyper-threading

3. Symmetrical Multi-Processing SMP -- Virtual SMP

4. Memory

One interesting point about VMWare ESX Server is that it does not use up much of the resources of the host computer. It has an overhead of only 3 to 8%. Compare that to the typical overhead of operating systems of 10 to 30%,

It also comes with a virtual network device -- VMXnet adapter.

VMWare ESX Server uses NUMA -- Non Uniform Memory Access and dynamic load balancing to use the host machine efficiently.

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