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Capacity Planning at Different Service Levels

One important thing that one should understand while discussing capacity planning, is the

type and extent of responsibility for a designated level of service provider, as well as for a service

consumer. The end users, who only use SaaS facility, are customers of the SaaS category service

providers. The SaaS category service provider may in turn be customer of some PaaS category

service provider, if not an independent computing vendor. Similarly, a PaaS category service

provider is either an independent vendor, or consumer of IaaS category service provider.

To explain the whole scenario in a simple form, let us consider three different companies

who are providers of different cloud services under some agreement. Company ‘A’ – IaaS facility

provider, company ‘B’ – PaaS facility provider, and company ‘C’ – SaaS provider (Figure 10.1).

The customers of company ‘C’ are application users (end users of computing). They can

take three ways to inform ‘C’ about capacity requirements. Case-1) can estimate their exact

business requirement and inform ‘C’. Case-2) Pass the entire responsibility of supporting

their demand to company ‘C’. Case-3) can take a middle path where business demand beyond

a certain (estimated) level will be supported by ‘C’. The choice and requirements have to


be mentioned as contract in SLA, so that ‘C’ can estimate capacity requirements and take

appropriate measures to arrange them. Company ‘C’, after accumulating all SLAs made with

its consumers has to estimate the future demands in a similar way. They also have the three

similar choices like its consumers.

Company ‘B’ has two options to maintain resource capacity to support their business

demand. With proper estimation, ‘B’ can keep few additional virtual servers (supplied by ‘A’)

under their hold as reserved resources, to support any unexpected raise in load to manage the

capacity themselves. The other option is to directly pass the ball (the responsibility of capacity

planning) to company ‘A’ keeping faith on their capability. They can take the middle path also,

by managing the capacity planning up-to a certain level by themselves and then passing the

responsibility to the infrastructure service provider in extreme cases. But, a reputed service

provider must handle the responsibility on their own, without depending on others.

The physical infrastructural resource management is the responsibility of the IaaS service

provider ‘A’. They have no option to pass the capacity planning task to other service providers

as providing physical resources is the ultimate responsibility of the IaaS provider ‘A’. The entire

scenario has been summarized in Figure 10.2.

Hence, the capacity planning task needs appropriate estimation of future demands at each

layer of cloud services. Although SaaS and PaaS consumers can not directly participate in capacity

planning activity, they should estimate business demand and inform their respective underlying

layers regarding future demand in advance. Each layer must remain well aware about possible

future demand to keep them-self ready.

If company ‘B’ remains uninformed (from its upper layers) and fails to support resource

demand beyond their planning, then it is likely that ‘A’ may fail to support the feature load

in many instances, if multiple among their consumers (like ‘B’) fail to do so and. IaaS facility

provider should be seen as the last line of defense, and the ball (the responsibility of supplying

infinite resources) should be not be allowed to pass on there.

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