What is VMware ESX 3?
by VCP Help on 14/01/09 at 7:49 pm
VMware ESX 3 is a hypervisor which means that it is a very thin layer of software that sits between the physical hardware and the various virtual machines. The hypervisor is responsible for translating requests such as disk access within a VM into actual disk access on the host regardless of whether the host is configured for a SAN, local SCSI, or NFS.
ESX is actually its own operating system. You boot a server from the CD and it installs ESX to the hard drive. The server then boots this ESX operating system. There is not any other operating system present as there is with Microsoft’s HyperV or products such as VMware Workstation. The fact that ESX is running directly on the “bare metal” means that it can offer performance and reliability that’s much higher than another product which must “talk” through a host operating system to get to the hardware. The down side to this is that ESX has its own drivers for the hardware so there is a fairly restricted set of hardware that it will run on. For example, you must have a supported SCSI disk controller.
ESX is available in a full version known currently as ESX 3.5 and also a free, reduced complexity version known as ESX 3i. 3i will run from a USB key or other form of storage but it seeks to reduce complexity by removing the Service Console which is a powerful command-line access method used to tweak, configure, and debug the regular ESX. Either version of ESX can be managed by Virtual Center.
You can think of ESX as the engine in the Virtual Infrastructure car. It does the heavy-lifting and actually provides the virtualization services.
