3.1.1 Service Design Parameters
As part of the design process for the Basic service offering, providers should give special consideration to key service settings and values in vCloud Director that can impact service performance and consistency levels for a subscriber’s organization virtual datacenter. Given the Pay-As-You-Go allocation model employed in this service, certain circumstances might arise that result in subscribers overcommitting resources over time. If not properly managed, performance for all application workloads could be negatively affected. The following table provides an example of these key service settings, values, and justifications.
Table 12. Resource Allocation Settings Example – Basic Service Offering
Resource Type | Value Range | Sample Setting | Justification |
CPU resources guaranteed | 0–100% | 0% | The percentage of CPU resources that are guaranteed to a virtual machine running within the target organization virtual datacenter. This option controls over-commitment of CPU resources. |
vCPU speed | 0–8GHz | 1GHz | This value defines what a virtual machine or vApp with one vCPU consumes at maximum when running within the target organization virtual datacenter. A virtual machine with two vCPUs consumes a maximum of twice this value. |
Memory resources guaranteed | 0–100% | 75% | The percentage of memory that is guaranteed to a virtual machine running within in the target virtual datacenter. This option controls overcommitment of memory resources. |
Maximum number of virtual machines | 1–Unlimited | Unlimited | A safeguard that allows control over the total number of vApps or virtual machines created by a subscriber within the target virtual datacenter |
In this example, the minimum vCPU speed setting is configured as 1GHz (1000 MHz), with a memory resource guarantee of 75%. CPU resource guarantees and limitations on the maximum number of virtual machines supported per tenant are optional and may be implemented at the provider’s discretion. The provider can use the combination of these settings to change overcommitment from aggressive levels (for example, resource guarantees set to <100%) to more conservative levels (for example, resource guarantees always set to 100%), depending on SLAs in place or fluctuating service loads.