ESXi Architecture



ESXi Architecture

VMware ESXi is the next-generation hypervisor, providing a new foundation for virtual infrastructure. This innovative architecture operates independently from any general-purpose operating system, offering improved security, increased reliability, and simplified management.

Functionally, ESXi is equivalent to ESX, offering the same levels of performance and scalability. However, the Linux-based service console has been removed, reducing the footprint to less than 32MB of memory.

Components of ESXi

Virtualization layer – also known as “VMkernel. 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:

  • Resource scheduling
  • I/O stacks
  • Device drivers

The main processes that run on top of VMkernel are:

Direct Console User Interface (DCUI)The Direct Console User Interface (DCUI) is the local user interface that is displayed only on the console of an ESXi system. Its main purpose is initial configuration and troubleshooting.

The DCUI configuration tasks include:

  • Set administrative password
  • Configure networking, if not done automatically with DHCP Troubleshooting tasks include:
  • Perform simple network tests
  • View logs
  • Restart agents
  • Restore defaults

Virtual Machine Monitor –  It is the process that provides the execution environment for a virtual machine, as well as a helper process known as VMX. Each running virtual machine has its own VMM and VMX process.

The Common Information Model (CIM) system: CIM provides industry standard framework for Hardware monitoring of compute resources. CIM is the interface that enables hardware-level management from remote applications via a set of standard APIs.

This Framework consists of CIM broker and set of CIM providers

CIM providersCIM provides run inside the ESXi system and provides management access to device drivers and underlying hardware.

CIM BrokerThe CIM broker takes information from all CIM providers and presents it to the outside world via standard APIs, including WS-MAN

User WorldsThe term “user world” refers to a process running in the VMkernel operating system.

Agents used by VMware to implement certain management capabilities have been ported from running in the service console to running in user worlds

  • Hostd – The hostd process provides a programmatic interface to VMkernel and is used by direct VI Client connections as well as the VI API. 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.
  • VpxaThe vpxa process is the agent used to connect to VirtualCenter. It runs as a special system user called vpxuser. It acts as the intermediary between the hostd agent and VirtualCenter.
  • FDMThe agent used to provide VMware HA capabilities has also been ported from running in the service console to running in its own user world.
  • SyslogA syslog daemon also runs as a user world. If you enable remote logging, that daemon forwards all the logs to the remote target in addition to putting them in local files.
  • A process that handles initial discovery of an iSCSI target, after which point all iSCSI traffic is handled by the VMkernel, just as it handles any other device driver. Note that the iSCSI network interface is the same as the main VMkernel network interface.


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I am VMware Solution Architect with 10+ Years of enriching experience in Datacenter Virtualization Technologies, Storage Area Networks and Software Defined Datacenter, Networking and Storage.
I hold Numerous certification including RHCE, CCNA, VCP4.0, VCP5.1, VCP5.5, vCloud and EMC certification.
While spending countless hours exploring the product inside and out and learning everything about it, Eventually I discovered my passion for teaching and helping others learn from my knowledge and experience so turned to Trainer cum Blogger to educate every single person keen to learn Virtualization.

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