VMware ESX Architecture.
In the original ESX architecture, the virtualization kernel (referred to as the vmkernel) is augmented with a management partition known as the console operating system (also known as COS or service console). The primary purpose of the Console OS is to provide a management interface into the host. Various VMware management agents are deployed in the Console OS, along with other infrastructure service agents (e.g. name service, time service, logging, etc). In this architecture, many customers deploy other agents from 3rd parties to provide particular functionality, such as hardware monitoring and system management. Furthermore, individual admin users log into the Console OS to run configuration and diagnostic commands and scripts.
- VMware agents run in Console OS
- Nearly all other management functionality provided by agents running in the Console OS
- Users must log into Console OS in order to run commands for configuration and diagnostics
VMware ESXi Architecture.
In the ESXi architecture, the Console OS 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 ESXi host greatly improves the security of the system.
- VMware agents ported to run directly on VMkernel
- Authorized 3rd party modules can also run in Vmkernel. These provide specific functionality
- Hardware monitoring
- Hardware drivers
- VMware components and third party components can be updated independently
- The “dual-image” approach lets you revert to prior image if desired
- Other capabilities necessary for integration into an enterprise datacenter are provided natively
- No other arbitrary code is allowed on the system