Once an organization has decided to embrace the benefits of cloud computing, there remain a number of questions to answer. The most important of these is whether to choose a public or a private cloud platform. From the perspective of a user within the organization, even a user who deploys and manages virtual servers, there’s little difference between the two.
However, from the perspective of the organization, there are considerable financial and operational differences, both in terms of ownership and control of the platform, and the cost structure.
Public clouds are multi-tenant systems that offer essentially unlimited scaling with on-demand pricing. An organization deploys virtual servers onto physical hardware which may be shared between several organizations. The virtualization layer ensures that each virtual server is completely isolated from others running on the same bare metal server, but the bare metal itself is shared.
Private cloud infrastructure, in contrast, is used by a single organization — only that organization can deploy virtual server resources on it. The organization pays for the bare metal hardware it needs, and can use the compute and storage to deploy and scale virtual servers if it has the physical infrastructure available to it. Scaling the physical layer is relatively straightforward with modern cloud technology, but not quite so quick and easy as deploying more servers on the public cloud.
A business should choose a private cloud platform if it wants to maintain complete control over its physical infrastructure and the data stored on it. This level of control may be important to an organization if it intends to run sensitive workloads on its cloud platform. Private cloud platforms may also be preferable if an organization needs to ensure it complies with some regulatory frameworks. It may be easier to achieve SOX, HIPAA, or PCI DSS compliance if the organization has full control of and insight into the hardware stack.
Under some circumstances, it may be more cost effective to choose a private cloud, especially for projects and applications that require long-running and consistent compute resources with predictable levels of server utilization.
The public cloud is an ideal platform when fast scaling or temporary infrastructure is of more importance than total control. If an organization expects that server and resource usage will be variable and subject to regular scaling, then a public cloud platform is likely to be the most cost effective option.
For simplicity’s sake, I’ve approached this article as if a choice has to be made between public and private cloud deployments. In reality, there’s no need to choose, and most enterprise organizations don’t choose — they use both public and private clouds because each benefits an organization in different ways. Hybrid cloud platforms that combine both public and private clouds are the most popular cloud modality among medium-to-large businesses.