VMware Architecture

VMware Architecture

VMkernel:- VMkernel is the core operat­ing system which provides means for running different processes on the  system, including management applications and agents as well as virtual machines. It also has control of all the hardware devices on the server, and manages resources for the applications.

What are the processes runs on VMkernel:-

DCUI, VMM, CIM, Different agents like HA agents

 DCUI- Direct Console User Interface- It is a BIOS like menu driven Esxi host con­figuration and management interface which is accessible through the console of the Esxi host. It is mainly used for initial Host configuration.

The virtual machine monitor (VMM)- It is the process that provides the execution environment for a virtual machine, as well as a helper process known as VMX.

The Common Information Model (CIM) system:- CIM is the interface that enables hardware-level management and monitoring from remote applications via a set of standard APIs.

What are user world processes-

The term “user world” refers to a set of process running above the VMkernel operating system.

This process are (i) HOSTD  (ii) VPXA (ii) VMware HA Agents (iv) SYSLOG deamon (v) NTP and SNMP

• HOSTD:- It is the process that authenticates users and keeps track of which users and groups have which privileges. It also allows you to create and manage local users. The HOSTD process provides a programmatic interface to VMkernel and is used by direct VI Client connections as well as the VI API.

• VPXA:-The vpxa process is the agent used to connect to VirtualCenter server. It runs as a special system user called vpxuser. It acts as the intermediary between the hostd agent and VCenter server.

What is the difference between VPXA, VPXD, HOSTD?

Hostd is demon or service runs in every ESXi host and performs major tasks like, VM power on, local user management etc. But when ESXi host joins in a vCenter server Vpxa agent gets activated and talk to Vpxd service which runs in vCenter server. So the conclusion is Vpxd talks to Vpxa and Vpxa talks to hostd, this is how Vpxd (vCenter demon) talks to hostd demon via Vpxa agents.

What initial tasks can be done by DCUI-

• Set administrative password

• Configure networking

• Perform simple network tests

• View logs

• Restart agents

• Restore defaults

Describe VMware System Image Design-

The ESXi system has two independent banks of memory, each of which stores a full system image, as a fail-safe for applying updates. When you upgrade the system, the new version is loaded into the inactive bank of memory, and the system is set to use the updated bank when it reboots. If any problem is detected during the boot process, the system automatically boots from the previously used bank of memory. You can also intervene manually at boot time to choose which image to use for that boot, so you can back out of an update if necessary.

At any given time, there are typically two versions of VI Client and two versions of VMware Tools in the store partition.