The first sense of cloud services covers a wide range of resources that a service provider delivers to customers via the internet, which, in this context, has broadly become known as the cloud. Characteristics of cloud services include self-provisioningand elasticity; that is, customers can provision services on an on-demand basis and shut them down when no longer necessary.
In addition, customers typically subscribe to cloud services, under a monthly billing arrangement, for example, rather than pay for software licenses and supporting server and network infrastructure upfront. In many transactions, this approach makes a cloud-based technology an operational expense, rather than a capital expense. From a management standpoint, cloud-based technology lets organizations access software, storage, compute and other IT infrastructure elements without the burden of maintaining and upgrading them.
The usage of cloud services has become closely associated with common cloud offerings, such as software as a service (SaaS), platform as a service (PaaS) and infrastructure as a service (IaaS).
SaaS is a software distribution model in which applications are hosted by a vendor or service provider and made available to customers over a network, typically the internet. Examples include G Suite — formerly Google Apps — Microsoft Office 365, Salesforceand Workday.
PaaS refers to the delivery of operating systems and associated services over the internet without downloads or installation. The approach lets customers create and deploy applications without having to invest in the underlying infrastructure. Examples include Amazon Web Services’ Elastic Beanstalk , Microsoft Azure — which refers to its PaaS offering as Cloud Services — and Salesforce’s App Cloud.
IaaS involves outsourcing the equipment used to support operations, including storage, hardware, servers and networking components, all of which are made accessible over a network. Examples include Amazon Web Services, IBM Bluemix and Microsoft Azure. SaaS, PaaS and IaaS are sometimes referred to collectively as the SPI model.