The debate on which cloud model is right for business often arises when an organization plans to migrate to the cloud. Both, the private and public cloud models have their own set of pros and cons. Any organization migrating to the cloud must first carefully understand public and private clouds for their benefits and disadvantages and finally decide their journey into the cloud.
The advent of cloud computing models is providing new directions for organizations in terms of scope and value. Organizations that are fully dependent on IT to meet business goals have understood the value of cloud computing for its availability, scalability, instant provisioning, virtualized resources and storage. Both private and public cloud models are available from cloud service providers but, first an organization thinking to deploy a cloud service must carefully examine the advantages and disadvantages of both private and public clouds.
Public clouds are hosted services available by cloud service providers on the internet. Organizations that use web servers or application systems where security and compliance requirements are not very rigid normally prefer to use public clouds. For example, public cloud services are available in the form of web based email, data storage or file transfers over the internet, online office applications, web hosting and so on. Public clouds are most suited for start-ups and small businesses because of minimal set up costs. The resources (servers, storage, etc.) are shared between multiple users publicly and the infrastructure, services and usage policies are managed by the service provider.
Contrary to the above, private clouds or enterprise clouds are used by organizations that have security, compliance and data privacy as their top priority. Private clouds are deployed inside firewalls and offer robust IT security for the organization. If a data center infrastructure is already available with the organization the private cloud can be implemented in-house. However, for having in-house private clouds the organization needs to invest heavily in running and maintaining the infrastructure which can result in significant capital expenditure. This can be a major setback for organizations thinking to reduce IT budgets. Private cloud services are also made available by cloud service providers or data centers. Examples of private cloud implementations can be easily found in areas such as banking and financial institutions, large enterprise organizations, government organizations, etc. where only authorized users are able to access the system.
It is essential to understand the intricacies of both these models before deciding to choose the appropriate model for the organization. The table below summarizes the main factors which can be used to determine between private and public clouds.
| Advantages |
| Private Clouds | Public Clouds |
Private cloud infrastructure is a dedicated infrastructure provided to one single organization or client. - Controls: Better controls for data, users and information assets.
- Cost: Initial investment for hardware is very high in case of an on-premise infrastructure.
- Security: The cloud belongs to a single client. Hence, the infrastructure and systems can be configured to provide high levels of security.
- Superior Performance: Normally private clouds are deployed inside the firewall of the organization’s intranet which ensures efficiency and good network performance.
- Easy Customization: The hardware and other resources can be customized easily by the company.
- Compliance: Compliance is achieved easily in private clouds.
| In public clouds the resources are shared between multiple clients and all the services are controlled by services provider. - Simple and easy: Public clouds are available as a service in the internet, they are easy to deploy.
- Cost: Initial investment is very low or nil.
- Less time: The IT resources and services are available immediately saving time for the company.
- No maintenance: The hardware and networks are maintained by the cloud services provider. Internal IT staffs have no responsibility in maintaining the infrastructure.
- No contracts: No long term commitment with service provider because public clouds are usually pay-as-you-go models.
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| Disadvantages |
- Cost: Costs are substantial in the case of building an on-premise private cloud. The running cost would include personnel cost and periodic hardware upgrade costs. In the case of outsourced private cloud, operating cost will include per resource usage and subject to change at the discretion of the service provider.
| - Lacks proper controls: The client has no control of data or infrastructure. There are issues of data privacy and integrity. The service level policies and compliances are completely enforced by the service provider.
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- Under-utilization: In some instances the resources subscribed can be under-utilized. Hence, optimizing the utilization of all resources is a challenge.
| - Performance: The performance of the network depends on the speed of the internet connectivity.
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- Capacity ceiling: Due to physical hardware limitations with the service provider, there could be a capacity ceiling to handle only certain amount of servers or storage.
| - Weak on Security: Since the hardware resource is shared between multiple users, IT security issues are more profound and data is vulnerable to thefts.
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- Vendor lock-in: This can be a major impediment in private cloud adoption especially when the hardware and infrastructure is outsourced. This is a service delivery technique where the client company is forced to continue with the same service provider, thus preventing the client to migrate to another vendor.
| - Customization: Customization of resources or services is not possible.
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Depending on the organization’s computing environment based on the above factors along with the levels of security and scalability needed, the organization can decide between deploying a private or public cloud.