What is impact of cloud on ITSM?

Cloud Service Models: (Defined by NIST)

Cloud Software as a Service (SaaS). The capability provided to the consumer is to use the provider‟s applications running on a cloud infrastructure. The applications are accessible from various client devices through a thin client interface such as a web browser (e.g., web-based email). The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, storage, or even individual application capabilities, with the possible exception of limited user-specific application configuration settings. 

Cloud Platform as a Service (PaaS). The capability provided to the consumer is to deploy onto the cloud infrastructure consumer-created or acquired applications created using programming languages and tools supported by the provider. The consumer does not manage or control the underlying cloud infrastructure including network, servers, operating systems, or storage, but has control over the deployed applications and possibly application hosting environment configurations. 

Cloud Infrastructure as a Service (IaaS). The capability provided to the consumer is to provision processing, storage, networks, and other fundamental computing resources where the consumer is able to deploy and run arbitrary software, which can include operating systems and applications. The consumer does not manage or control the underlying cloud infrastructure but has control over operating systems, storage, deployed applications, and possibly limited control of select networking components (e.g., host firewalls).

The relationship between cloud and ITSM

According to the Information Technology Infrastructure Library (ITIL®) there are four phases in the lifecycle of a service or application: service strategy design, service transition, service operation, and continual service improvement. The four lifecycle phases are more critical for cloud computing than they are for traditional computing because most of the activity occurs remotely, which reduces the amount of control that can be levered locally and leads to problems, unexpected outages or unmet expectations. For example, should the cloud supplier include their customers in their change management process? If not, who is culpable if a change fails causing an outage? Or what happens if the workload demand is wrongly calculated? Could this lead to unexpected costs being incurred?

Successful cloud computing starts with careful strategic planning to decide which service strategy to adopt (e.g. to utilize cloud computing as a strategy to improve a current service or to implement a new service). From the service management viewpoint this encompasses portfolio management, demand management, and financial management. Portfolio management provides a description of the cloud candidate, while demand management calculates the workload and financial management calculates the costs required to supply and meet the workload demands. If these calculations are inaccurate or ignored then not only could the wrong delivery service be selected but also the incorrect charging algorithm could be adopted. Service strategy is essential because it is the foundation stone for cloud computing.