5. vCloud Resource Design : 5.3 Provider Virtual Datacenter
5.3 Provider Virtual Datacenter
The virtual datacenter is a new construct that represents the standard container for a pool of compute and storage resources. There are two types of virtual datacenters: provider and organization. Provider virtual datacenters are composed of resource pools and datastores from a single vCenter Server. When creating a provider virtual datacenter, observe the following guidelines:
*Define the standard units of consumption. Variance in virtual datacenter allocations decreases manageability. Look at existing trends to determine common container sizes.
*Resource pools can map to a single provider virtual datacenter.
*If enough capacity exists, map the root resource pool of the cluster to provider virtual datacenters. This simplifies resource management. If the cluster expands, the backed provider virtual datacenter automatically grows as well. This is not the case if a standard resource pool is used. Multiple parent-level resource pools can add unnecessary complexity and lead to unpredictable results or inefficient use of resources if the reservations are not set appropriately.
*Create multiple provider virtual datacenters to differentiate computing levels or performance characteristics of a service offering. An example of differentiating by availability would be N+1 for a Bronze provider virtual datacenter versus N+2 for a Silver provider virtual datacenter.
*One or more datastores can be attached to a provider virtual datacenter. Multiple provider virtual datacenters can share the same datastore. For isolation and predictable storage growth, do not attach the same datastore to multiple provider virtual datacenters.
*Storage tiering is not possible within a provider virtual datacenter. Instead, supply tiered pools of storage through multiple provider virtual datacenters.
*As the level of expected consumption increases for a given provider virtual datacenter, add additional hosts to the cluster from vCenter Server and attach more datastores.
*As the number of hosts backing a provider virtual datacenter approaches the halfway mark of cluster limits, implement controls to preserve headroom and avoid reaching the cluster limits. For example, restrict the creation of additional tenants for this virtual datacenter and add additional hosts to accommodate increased resource demand for the existing tenants.
*If the cluster backing a provider virtual datacenter has reached the maximum number of hosts, create a new provider virtual datacenter associated with a separate cluster.
See Service Definitions for guidance on provider virtual datacenter sizing. Consider the following:
*Expected number of virtual machines.
*Size of virtual machines (CPU, memory, storage).
In some cases, a “special purpose" provider virtual datacenter dedicated to a single workload type might be needed. Special use case provider virtual datacenters are an example of what makes vCloud computing so flexible and powerful. The primary driver behind the need for a special purpose virtual datacenter is to satisfy the license restrictions imposed by software vendors that stipulate that all the processors that might run specific software must be licensed for it, regardless of whether they actually are running that software.
To keep licensing costs down while meeting the EULA requirements of such software vendors, create a purpose-specific provider virtual datacenter backed by the minimum number of CPU sockets needed to achieve performance requirements. Create a corresponding organization virtual datacenter per tenant, and provide descriptive naming to guide users to deploy workloads accordingly.