The focus of enterprises lies increasingly on higher flexibility and indeed agility, largely due to the uncertain economic environment and high levels of business risk to date. This also puts much pressure on CIOs, who need to ensure ongoing challenges and shifts are met with the adequate IT operations. Besides, strategic and financial IT objectives must be met with cost and operational efficiency, in particular with IT resources that allow scalability and a high degree of flexibility and finally, greener IT operations.
Some analysts and vendors define cloud services narrowly as an updated version of utility computing: basically virtual servers available over the Internet. Others go very broad, arguing anything you consume outside the firewall is "in the cloud", including conventional outsourcing. Many market participants are already responding to the "media" overburdening of the cloud concept; sometimes they avoid the term altogether or replace it.
First of all, but very important, is that cloud services, in contrast to classic hosting or colocation services, are multitenant platforms and allow on-demand usage-base billing. Multitenant can mean here serving several different companies with the same platform, or, in the case of a private cloud, serving different divisions, departments or user groups within a company. There are three main categories of cloud services: SaaS, PaaS and IaaS.
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