Private vs. Public Cloud Computing

Cloud computing has found its way into many organizations as business leaders and IT departments look to capitalize on the many benefits that cloud offers. As your company considers moving all or part of its IT operation to the cloud, a key decision is whether to rely on public cloud, private cloud, or a combination. Finalizing a cloud strategy must start with understanding your objectives and how they best align with the value each offering can provide.

The public cloud can be characterized by IT resources delivered via the Internet using a standardized, self-service, pay-per-use methodology. Public clouds are designed to provide compute resources virtually at will – similar to that of a utility. Public clouds are highly standardized, allow limited customization, and their respective resources can be oversubscribed and massively shared. Workloads requiring inexpensive storage or compute cycles where known response time to the user community is not critical can be a fit with the public cloud…


Private clouds offer scalable compute resources similar to that of public clouds, but in a more controlled environment. Private cloud providers, especially those with managed services around hosted applications, bring insight into the workload and impacts to the infrastructure. Private cloud providers have the flexibility to customize solutions to meet security and performance requirements. They can also identify where customer data is stored, as in a specific data center or country. The setup allows for more customization and delivers a higher-degree of privacy and security.

As you determine which methodology makes the most sense for your business, here are the three major assessment areas to consider and help guide you in your decision.

Availability Comparison
When it comes to accessing more computing resources, both private and public clouds are designed to provide highly elastic compute power and data storage. When you need more resources, you can request and receive them almost immediately. However, there is a tradeoff since public cloud customers are competing for the same pool of resources. This can impact the cloud experience with unexpected bursts in demand or seasonal type activity. Private cloud providers are able to introduce a level of segmentation to protect workload for a predictable user experience, but still provide the resiliency and flexibility the cloud provides for availability.

Like the public cloud, private cloud services rely on virtualized computing resources to provide elasticity and scale. However, each customer is given its own private pool of resources rather than sharing them. Resources can be expanded, but it is done in a more controlled manner.

Private clouds can offer a degree of elasticity, but also a higher degree of stability than public clouds. This is why private clouds are more attractive for production environments, where the ability to scale is important, but uptime is just as critical.

Another key component to availability is access to the compute resources in the cloud. Traditionally access to the public cloud is done via the Internet. Private cloud providers can be more accommodating for those customers that want to leverage the private line wide area networks currently deployed. With the potential to leverage the Internet as an alternate path to the environment with a dynamic reroute across a hardware-based VPN solution should any carrier issues arise.

Security Comparison
Like any utility, public clouds are easily accessible by the masses. Security controls are in place, but with limits as to how much they can control risk. Public clouds thus can be attractive targets for hackers who enjoy the challenge of breaking into public clouds, which they can then use anonymously to attack other sites.

Private clouds offer more security since computing resources are more logically separated. Where private cloud providers are hosting known applications, tighter security at the network layer can be deployed to further reduce the risk of unnecessary traffic. Security zones and firewall rule sets can be deployed to address multi-tenancy concerns of cloud offerings.

As stated above on availability, there is also a higher degree of security with access to the cloud resources and connectivity. Companies accessing the private cloud via virtual private networks or dedicated circuit can beneficial for firms in highly regulated arenas where enterprise data needs to be protected carefully to demonstrate financial and operational stability to regulators and investors.

Control Comparison
By design, public clouds give users direct control over the volume of computing resources provisioned: you simply provision what you need when you need it. But, you cannot control what other customers in the resource pool access, which may affect your environment and minimize performance predictability.

Public clouds also make modifications to the underlying infrastructure more challenging. For example, if a technical change is needed, such as a software patch or hardware swap, that change impacts everyone because customers are not isolated from each other. Also there is no coordination with the application MTRs running on top of the infrastructure and how the updates may impact functionality. In addition, customers must diligently control the level of computing resources they contract for, monitoring the resources they need and use, and then requesting resources to be turned off when no longer needed; providing less control over computing costs.

Conversely, a private cloud gives you more control over the performance of the technology environment. Customers can work jointly with private cloud providers to adhere to change control policies that may already be established. Resource allocation and load balancing can be finely tuned based on each customer’s environment, usage patterns, and resource consumption.

The environment is also more resilient as more sophisticated redundancy and failover capabilities can be incorporated. Private clouds can also more easily provide degrees of data backup for various data retention policies. Customized solutions for disaster recovery customers based on recovery point and recovery time objectives can all be taken into the design criteria for a solution.

Utility and Consistency Requirements Dictate the Ultimate Choice
If your business requires basic computing resources where uptime and system control are not mission-critical, public clouds can serve as an inexpensive method for rapid provisioning of IT infrastructure. As is the case with most utility companies, public cloud providers offer a serviceable, raw platform at a low cost.

But if you want scalability benefits with more control, private cloud services are much more likely to meet your requirements. Private clouds essentially provide a more consistent experience because providers are more in tune with how their customers use the infrastructure and can plan accordingly. This allows for application performance SLAs where customers can shift their focus away from managing the infrastructure and concentrate on their business. Customers receive the benefits of scale and can leverage the cost savings that cloud provides without all the management issues.