2. vCloud Architecture : 2.3 vCloud Infrastructure Logical Design
   
2.3 vCloud Infrastructure Logical Design
When architecting a VMware vCloud infrastructure logical design, VMware recommends using a building block approach to provide a scalable, resilient architecture. The two top-level logical building blocks are virtual management clusters and resource groups. The segregation of resources allocated for management functions from resources dedicated to user-requested workloads is achieved using management clusters and resource groups.
*A vSphere management cluster contains both the core and optional components and services needed to run the vCloud. This includes core vCloud components such as VMware vCenter Server, vCloud Director, vCenter Chargeback Manager, vCenter Orchestrator, and optional components such the VMware vCenter Operations Suite and vFabric Application Director.
*Resource groups represent vCloud dedicated resources for end-user consumption. Each resource group consists of vSphere clusters (VMware vSphere hosts managed by a vCenter Server), and is under the control of vCloud Director. vCloud Director can manage the resources of multiple resource groups.
Reasons for separate management and resource clusters include the following:
*Separation of duties – In a vCloud infrastructure you typically have at least two types of administrator: infrastructure (vSphere) administrator and a vCloud administrator. By separating the management cluster from resource groups, clear separation of duties is established to enforce administrative boundaries, limiting the actions that can be performed in the vSphere clusters that comprise a resource group.
There are actions that can be performed on a resource group through the vSphere Client that should not be carried out by an administrator. These include:
*Editing virtual machine properties.
*Renaming virtual machine.
*Disabling DRS.
*Deleting or renaming resource pools.
*Changing networking properties.
*Renaming datastores.
*Changing or renaming folders.
This is not an exhaustive list, but it covers some of the detrimental actions a vCenter administrator could perform on a vCloud resource group. The inherent risk highlights the architectural importance of maintaining separation of management clusters and resource groups.
*Resource consumptionVirtual machines deployed into resource groups that are not managed by vCloud Director consume resources that are allocated for a particular vCloud virtual datacenter. This skews the resource utilization and consumption metrics available to the vCloud.
*Scalability and configuration maximumsHaving separate vSphere clusters to manage end-user-consumed compute resources increases resource group scalability. A vCloud environment must conform to vSphere scalability and configuration maximums. Having dedicated resource group vSphere clusters means that the scalability of vCloud user resources is not affected by management workloads.
*Availability – A virtual management cluster allows the use of VMware vSphere HA and DRS to provide enhanced availability to all management components. A separate management cluster enables this protection in a more granular fashion to satisfy management-specific SLAs. It also increases upgrade flexibility because management cluster upgrades are not tied to resource group upgrades.
*Prevents denial-of-service attacks or intensive provisioning activity on the resource groups from affecting management component availability.
*Disaster Recovery facilitation – Having separate management clusters and resource groups simplifies the design and implementation of vCloud Disaster Recovery. The vCloud Disaster Recovery solution uses an SRM-managed vSphere cluster that contains all of the vCloud infrastructure management components. This solution is explained in further detail in Appendix C: vCloud Suite Disaster Recovery.
*Support and troubleshooting – To facilitate troubleshooting and problem resolution, management components are strictly contained in a relatively small and manageable cluster. Running management components within large clusters that contain mixed resource and management components makes it difficult to diagnose issues with management components efficiently.
*Separation of management components from the resources they are managing. This helps avoid inadvertent changes to vCloud Director-created entities through the vSphere Client.
Figure 3. vCloud Logical Architecture Overview
 
Achieving economies of scale means scaling vCloud resources in a consistent and predictable manner. Follow applicable, recommended practices when deploying the underlying vSphere infrastructure and other vCloud components.