5. Creating and Managing vApps : 5.6 Establishing Service Levels : 5.6.3 vCloud Considerations for Service Level Agreements
5.6.3 vCloud Considerations for Service Level Agreements
SLAs are required to provide efficiency and accountability at every layer for both external providers and internal IT groups. Managing SLAs in every layer helps to isolate systemic problems and eliminate delays.
There are inter-relationships between SLAs at different vCloud layers, and any change in quality of the service or breach of one of the lower vCloud layers might impact multiple SLAs at a higher vCloud layer. Using the previous example of an organization with an IaaS layer hosted by a public vCloud provider and PaaS and SaaS layers maintained internally, an SLA performance breach resulting in external vCloud providers unable to support operating system performance needs would propagate problems to the SaaS layer, decreasing application performance and response time for business users.
Business needs are continuously evolving, as are business requirements for a vCloud. SLAs must be continually updated to reflect current business requirements. In the previous example, adding a thousand new business users to a particular application is likely to increase the criticality and cause the application to be deemed mission-critical. This business change means that corresponding SLAs supporting the application might require revision for increased uptime and availability. This, in turn, leads to increased demands at the IaaS layer, requiring revisions to SLAs with an external IaaS provider as well.