An introduction to the components of VMware vSphere helps you to understand the parts and how they interact.

VMware vSphere includes the following components.

VMware® ESX and VMware® ESXi

A virtualization layer run on physical servers that abstracts processor, memory, storage, and resources into multiple virtual machines.

Two versions of ESX are available:

VMware ESX 4.1 contains a built-in service console. It is available as an installable CD-ROM boot image.

VMware ESXi 4.1 does not contain a service console. It is available in two forms: VMware ESXi 4.1 Embedded and VMware ESXi 4.1 Installable. ESXi 4.1 Embedded is firmware that is built into a server’s physical hardware. ESXi 4.1 Installable is software that is available as an installable CD-ROM boot image. You install the ESXi 4.1 Installable software onto a server’s hard drive.

VMware® vCenter Server

The central point for configuring, provisioning, and managing virtualized IT environments.

VMware® vSphere Client

An interface that allows users to connect remotely to vCenter Server or ESX/ESXi from any Windows PC.

VMware® vSphere Web Access

A Web interface that allows virtual machine management and access to remote consoles.

VMware® Virtual Machine File System (VMFS)

A high performance cluster file system for ESX/ESXi virtual machines.

VMware® Virtual SMP

Feature that enables a single virtual machine to use multiple physical processors simultaneously.

VMware® vMotion and Storage vMotion

VMware vMotion enables the live migration of running virtual machines from one physical server to another with zero down time, continuous service availability, and complete transaction integrity. Storage vMotion enables the migration of virtual machine files from one datastore to another without service interruption. You can choose to place the virtual machine and all its disks in a single location, or select separate locations for the virtual machine configuration file and each virtual disk. The virtual machine remains on the same host during Storage vMotion.

Migration with vMotion lets you move a powered-on virtual machine to a new host. Migration with vMotion allows you to move a virtual machine to a new host without any interruption in the availability of the virtual machine. Migration with vMotion cannot be used to move virtual machines from one datacenter to another.

Migration with Storage vMotion lets you move the virtual disks or configuration file of a powered-on virtual machine to a new datastore. Migration with Storage vMotion allows you to move a virtual machine's storage without any interruption in the availability of the virtual machine.

VMware® High Availability (HA)

Feature that provides high availability for virtual machines. If a server fails, affected virtual machines are restarted on other production servers that have spare capacity.

VMware® Distributed Resource Scheduler (DRS)

Feature that allocates and balances computing capacity dynamically across collections of hardware resources for virtual machines. This feature includes distributed power management (DPM) capabilities that enable a datacenter to significantly reduce its power consumption.

VMware® vSphere SDK

Feature that provides a standard interface for VMware and third-party solutions to access the VMware vSphere.

VMware® Fault Tolerance

When Fault Tolerance is enabled for a virtual machine, a secondary copy of the original (or primary) virtual machine is created. All actions completed on the primary virtual machine are also applied to the secondary virtual machine. If the primary virtual machine becomes unavailable, the secondary machine becomes active, providing continuous availability.

vNetwork Distributed Switch (vDS)

Feature that includes a distributed virtual switch (vDS), which spans many ESX/ESXi hosts enabling significant reduction of on-going network maintenance activities and increasing network capacity. This allows virtual machines to maintain consistent network configuration as they migrate across multiple hosts.

Host Profiles

Feature that simplifies host configuration management through user-defined configuration policies. The host profile policies capture the blueprint of a known, validated host configuration and use this to configure networking, storage, security, and other settings across multiple hosts. The host profile policies also monitor compliance to standard host configuration settings across the datacenter. Host profiles reduce manual steps involved in configuring a host and can help maintain consistency and correctness across the datacenter.

Pluggable Storage Architecture (PSA)

A storage partner plug-in framework that enables greater array certification flexibility and improved array-optimized performance. PSA is a multipath I/O framework allowing storage partners to enable their array asynchronously to ESX release schedules. VMware partners can deliver performance-enhancing multipath load-balancing behaviors that are optimized for each array.