VMware vSphere ESX and ESXi Info Center

VMware vSphere Architectures Compared

vSphere ESX Architecture. In the original vSphere ESX architecture, the virtualization kernel (referred to as the VMkernel) was augmented with a management partition known as the console operating system (COS or service console). The primary purpose of the COS was to provide a management interface into the host. Various VMware management agents were deployed in the COS, along with other infrastructure service agents (e.g. name service, time service, logging, etc). In this architecture, many customers deployed other agents from 3rd parties to provide particular functionality, such as hardware monitoring and system management. Furthermore, individual admin users logged into the COS to run configuration and diagnostic commands and scripts.

New vSphere ESXi Architecture. In the new vSphere ESXi architecture, the COS has been removed and all of the VMware agents run directly on the VMkernel. Infrastructure services are provided natively through modules included with the VMkernel. Other authorized 3rd party modules , such as hardware drivers and hardware monitoring components, can run in VMkernel as well. Only modules that have been digitally signed by VMware are allowed on the system, creating a tightly locked-down architecture. Preventing arbitrary code from running on the vSphere host greatly improves the security of the system.

Comparing the legacy and new vSphere Architectures

Comparing the previous generation ESX architecture with the new innovative ESXi architecture:

See the KB article for a detailed comparison.