Explain ESXi and vCenter Server Architecture VMware vSphere is a virtualization platform that consists of two primary products: VMware ESXi and VMware vCenter Server. ESXi is the hypervisor and installs on bare-metal hardware without the need for an additional underlying operating system. The hypervisor provides physical hardware resources dynamically to virtual machines as needed to support the operation of the virtual machines. vCenter Server is a service that acts as a central administrator for ESXi hosts that are connected on a network. vCenter Server allows you to pool and manage the resources of multiple hosts. | |||||||||||||||||||||||||||||||||
vCenter Server comes in two versions: Standard (up to three ESX servers) and Foundation (large-scale vCenter Server deployments). vCenter Server performs the following three key functions:
vSphere features such as VMotion, Storage VMotion, Distributed Resource Scheduler, VMware High Availability and Fault Tolerance require vCenter Server.
ESXi is the hypervisor or virtualization platform on which you create and run virtual machines in a vSphere environment. | |||||||||||||||||||||||||||||||||
An abbreviated history of ESXi:
The size of the ESXi (5.0) image is 144 MB on disk. This size may increase with future updates, fixes, drivers and functionality. The compact architecture is designed for integration directly into virtualization-optimized server hardware, enabling rapid installation, configuration, and deployment. On ESXi hosts, the management component is based on a limited implementation of the POSIX environment and interface and an integrated set of busybox tools. The VMware ESXi architecture comprises the underlying operating system, called VMkernel, and processes that run on top of it. VMkernel provides means for running all processes on the system, including management applications and agents as well as virtual machines. It has control of all hardware devices on the server, and manages resources for the applications. The main processes that run on top of VMkernel are:
VMkernel is a POSIX-like operating system developed by VMware and provides certain functionality similar to that found in other operating systems, such as process creation and control, signals, file system, and process threads. It is designed specifically to support running multiple virtual machines and provides such core functionality as:
This file system is independent of the VMware VMFS file system used to store virtual machines. The in-memory file system does not persist when the power is shut down, as a result log files do not survive a reboot. ESXi has the ability to configure a remote syslog server, enabling you to save all log information on an external system. The term “user world” refers to a process running in the VMkernel operating system. The environment in which a user world runs is limited compared to what would be found in a general-purpose POSIX-compliant operating system such as Linux. The DCUI is the local user interface that is displayed only on the console of an ESXi system. It provides a BIOS-like, menu-driven interface for interacting with the system. Its main purpose is initial configuration and troubleshooting tasks. The intention is that the user carries out minimum configuration with the DCUI, then uses a remote management tool to perform all other configuration and ongoing management tasks. Agents used by VMware (e.g. hostd, vpxa) to implement certain management capabilities are run in “user worlds”. A number of network ports are open on ESXi, such as: 80, 443 (reverse proxy), 427 (service location protocol), 902, 5989. |
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Tuesday, April 17, 2018
Explain ESXi and vCenter Server Architecture
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