A typical VMware vSphere data center consists of physical building blocks such as x86 virtualization servers, storage networks and arrays, IP networks, a management server, and desktop clients.

The vSphere data center includes the following components.

ESXi Hosts
Industry standard x86 servers that run ESXi on the bare metal. ESXi software provides resources for and runs the virtual machines. You can group a number of similarly configured x86 servers with connections to the same network and storage subsystems. This grouping creates an aggregate set of resources in the virtual environment, called a cluster.
Storage networks and arrays
VMware vSphere uses Fibre Channel SAN arrays, iSCSI SAN arrays, and NAS arrays to meet different data center storage needs. With storage area networks, you can connect and share storage arrays between groups of servers. This arrangement allows aggregation of the storage resources and provides more flexibility in provisioning them to virtual machines. For detailed information, see vSphere Storage.
IP networks
Each compute server can have multiple physical network adapters to provide high bandwidth and reliable networking to the entire VMware vSphere data center. For detailed information, see vSphere Networking.
vCenter Server
vCenter Server provides a single point of control to the data center. It provides essential data center services such as access control, performance monitoring, and configuration. It unifies the resources from the individual computing servers to be shared among virtual machines in the entire data center. It manages the assignment of virtual machines to the ESXi hosts and the assignment of resources to the virtual machines within a given computing server. These assignments are based on the policies that the system administrator sets.

Compute servers continue to function even if vCenter Server becomes unreachable (for example, if the network is severed). The ESXi hosts can be managed separately and continue to run the virtual machines assigned to them based on the resource assignment that was last set. After connection to vCenter Server is restored, it can manage the data center as a whole again.

Management clients
VMware vSphere provides several interfaces for data center management and virtual machine access. These interfaces include vSphere Client for access through a web browser or vSphere Command-Line Interface (vSphere CLI).