The salient feature of the Cisco UCS platform is stateless computing. In the Cisco UCS platform, none of the computer peripherals consume the hardware's burned-in identities. Rather, all the unique characteristics are extracted from identity and resource pools, which reside on the Fabric Interconnects (FIs) and are managed using UCSM. These resource and identity pools are defined in an XML format, which makes them extremely portable and easily modifiable. UCS computers and peripherals extract these identities from UCSM in the form of a service profile. A service profile has all the server identities, including UUIDs, MACs, WWNNs/WWPNs, firmware versions, BIOS settings, and other server settings. A service profile is associated with the physical server using a customized Linux OS that assigns all the settings in a service profile to the physical server. In case of server failure, if the failed server needs to be removed and the replacement server has to be associated with the existing service profile of the failed server. In this service profile association process, the new server will automatically pick up all the identities of the failed server and the operating system or applications dependent upon these identities will not observe any change in the hardware. In case of peripheral failure, the replacement peripheral will automatically acquire the identities of the failed component. This greatly improves the time required to recover a system in case of a failure.
Using service profiles with the identity and resource pools also greatly improves the server provisioning effort. A service profile with all the settings can be prepared in advance while an administrator is waiting for the delivery of the physical server. The administrator can create service profile templates that can be used to create hundreds of service profiles; these profiles can be associated with the physical servers with the same hardware specifications. Creating a server template is highly recommended as it greatly reduces the time required for server provisioning. This is because a template can be created once and used for any number of physical servers with the same hardware.
Server identity and resource pools are created using UCSM. In order to better organize, it is possible to define as many pools as needed in each category. Keep in mind that each defined resource will consume space in the UCSM database. It is, therefore, best practice to create identity and resource pool ranges based on the current and near-future assessments.
For larger deployments, it is best practice to define a hierarchy of resources in the UCSM based on geographical, departmental, or other criteria; for example, a hierarchy can be defined based on different departments. This hierarchy is defined as an organization, and the resource pools can be created for each organizational unit. In the UCSM, the main organization unit is root, and further sub-organizations can be defined under this organization. The only consideration to be kept in mind is that pools defined under one organizational unit can't be migrated to other organizational units unless they are deleted first and then created again where required.
The following diagram shows how identity and resource pools provide unique features to a stateless blade server and components such as the mezzanine card:
