In the traditional hosted application model, the vendor provides the entire infrastructure for a customer to run his applications. Often, this entails housing dedicated hardware that is purchased or leased for that specific application. The IaaS model also provides the infrastructure to run the applications, but the cloud computing approach makes it possible to offer a pay-per-use model and to scale the service depending on demand. Prom the laaS providers perspective, it can build an infrastructure that handles the peaks and troughs of its customers’ demands and add new capacity as the overall demand increases. Similarly, in a hosted application model, the laaS vendor can cover application hosting only, or can extend to other services (such as application support, application development, and enhancements) and can support the more comprehensive outsourcing of IT.
The laaS model is similar to utility computing, in which the basic idea is to offer computing services in the same way as utilities. That is, you pay for the amount of processing power, disk space, and so on that you actually consume. laaS is typically a service associated with cloud computing and refers to online services that abstract the user from the details of infrastructure, including physical computing resources, location, data partitioning, scaling, security, backup, and so on. In cloud computing, the provider is in complete control of the infrastructure. Utility computing users, conversely, seek a service that allows them to deploy, manage, and scale online services using the provider’s resources and pay for resources the customer consumes. However, the customer wants to be in control of the geographic location of the infrastructure and what runs on each server.
Features available for a typical IaaS system include:
The ability to scale infrastructure requirements, such as computing resources, memory, and storage (in near-real-time speeds) based on usage requirements
Pay as you go
The ability to purchase the exact amount of infrastructure required at any specific time
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