VMware ESX

With the rapidly growing interest in running production applications on virtualized servers, VMware’s flagship ESX Server virtualization product poses a serious challenge to Windows as the controlling OS.

Unlike Microsoft Virtual Server 2005 and VMware’s lower-end GSX product, which create a host OS by installing a virtualization layer on top of a conventional OS (GSX can install on either Windows or Linux, while Microsoft’s Virtual Server installs only on Windows), ESX is a proprietary OS built specifically to host virtual machines (VMs). Because ESX is specially tailored for the host OS role, it dispenses with most of the overhead needed by a general purpose OS, thereby making it highly compact, more secure, and faster.

ESX consists of a small proprietary kernel and a Linux-based “service console” that runs on top of it and provides a means of managing and monitoring the kernel. The kernel itself has no user interface and supports only one proprietary API, the one used to communicate with the service console. The service console supports VMware’s management tools and can support hardware management agents from Dell, Hewlett-Packard, or IBM and tape backup agents from CommVault, Computer Associates, IBM, Legato, or Symantec.