Topic: VMware ESX Server

Description: VMware ESX Server is an enterprise-level virtualization product offered by VMware, Inc., a division of EMC Corporation. ESX Server is a component of VMware's larger offering, VMware Infrastructure, which adds management and reliability services to the core server product. The basic server requires some form of persistent storage - typically an array of hard disk drives - for storing the virtualization kernel and support files. A variant of this design, called ESX Server ESXi Embedded, does away with the first requirement by moving the server kernels into a dedicated hardware device. Both variants support the services offered by Virtual Infrastructure.

VMware states that the ESX Server product runs on "bare metal". In contrast to other VMware products, it does not run atop a third-party operating system, but instead includes its own kernel. Up through the current ESX version 3.5, a Linux kernel is started first and is used to load a variety of specialized virtualization components, including VMware's 'vmkernel' component. This previously-booted Linux kernel then becomes the first running virtual machine and is called the service console. Thus, at normal run-time, the vmkernel is running on the bare computer and the Linux-based service console runs as the first virtual machine (and cannot be terminated or shutdown without shutting down the entire system).
In terms of performance, virtualization imposes a cost in the additional work the CPU has to perform to virtualize the underlying hardware. Instructions that perform this extra work, and other activities that require virtualization, tend to lie in operating system calls. In an unmodified operating system, OS calls introduce the greatest portion of virtualization overhead.
Paravirtualization or other virtualization techniques may help with these issues. VMware and XenSource invented the Virtual Machine Interface for this purpose, and selected operating systems currently support this. A comparision between full virtualization and paravirtualization for the ESX Server shows that in some cases paravirtualization is much faster.

Applications: VMware Infrastructure 3, which includes the following programs:
  • VMware ESX 3.5 or VMware ESXi 3.5
  • VMware vCenter Server Agent
  • VMware Virtual Machine File System (VMFS)
  • VMware Virtual Symmetric Multi-Processing (vSMP)
  • VMware Update Manager (Guest and Host)
  • VMware VMotion + Storage VMotion
  • VMware High Availability (HA)
  • VMware Distributed Resource Scheduler (DRS)
  • VMware Consolidated Backup

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