Public Cloud vs. Private Cloud

In the relatively short history of cloud computing so far, a handful of recurring topics have cemented themselves as major parts of the overall cloud discourse. These range from debates over vendors' offerings and quality of service to discussions regarding optimal use cases. One of the most common umbrella topics is deployment, and the comparison of public cloud vs. private cloud often comes up in those discussions.
Like many things in technology—and life—this is not a strictly black-and-white issue. Different enterprises will have different answers as to why they choose one or the other, or opt for a combination of both. It's therefore impossible to say that a public cloud is definitively better than its private counterpart, or vice versa. But what we can do regarding this debate is define the two deployment scenarios properly and look at their various pros, cons, and ideal uses.

public cloud vs private cloud

The main difference between public cloud and private cloud

If you had to quickly define the primary difference between a public cloud deployment and a private cloud computing service, it's related to who uses it.

A public cloud solution, such as Amazon Web Services (AWS), Microsoft Azure, or Google Cloud, is readily available to any enterprise or individual that pays for a subscription. Many different companies will have their data and application code on the same servers offered by the same cloud service provider at any given time.

Usually, this sharing of foundational infrastructure as a service (IaaS) servers causes no trouble for anyone — although when the providers of public cloud solutions do experience downtime, multiple enterprises are affected. You've probably experienced some version of this yourself; for example, when Google or Microsoft has an outage, all of your Workspace or Office 365 apps are temporarily unavailable.

On the other end of the spectrum is private cloud, which is the sole province of one customer. Providers of private cloud services may offer highly customized cloud infrastructure to individual enterprise clients, which they don't share with others.

Alternatively, an enterprise could build up cloud infrastructure and host it in its own data center, strictly using on-premises networking, security, hardware, and computing resources, and call that private cloud. But many might simply call that on-premises infrastructure. Also, a vendor offering software as a service (SaaS) or platform as a service (PaaS) through a VMWare conduit to one customer might refer to that as a type of private cloud deployment.

How do hybrid cloud and multi-cloud fit in?

If you're somewhat new to all of this, don't be fazed by all of the jargon flying around — these terms fall within the purview of public and private cloud, rather than being something else entirely.

  • Hybrid cloud often refers to the pairing of public cloud resources from a public cloud vendor with on-premises infrastructure. Alternatively, some vendors define a hybrid cloud solution as the combination of public cloud computing services with managed private cloud services for single customers.
  • Multi-cloud means using multiple public clouds, each one usually from a different provider. If the multi-cloud deployment is paired with an on-premises data center, then it is a hybrid multi-cloud. 

Using multiple public clouds has become quite popular: In a 2020 study conducted by IDG, 55% of the organizations queried confirmed that they had multi-cloud setups, and 21% of the respondents claimed to be using three clouds or more. Additionally, IDC expected more than 90% of companies worldwide were using some combination of public cloud and on-premises resources at the end of 2021.

The pros and cons of public and private clouds

Both the public and private cloud deployment models have distinct advantages and undeniable shortcomings. Let's take a closer look at each:

Public cloud

First, let's see those advantages:

  • Potential cost savings: Because you aren't purchasing your own hardware and software upfront to use public cloud services—or spending as much on compute, storage, security, and networking as you might if you managed these operations yourself—there's opportunity for notable cost savings.
  • No management and maintenance: Both are handled by the CSP, leaving internal IT teams to focus on other business priorities.
  • Rapid elasticity: You can add or remove resources in real time based on the day-to-day needs of the enterprise, without disrupting performance.
  • Lower-cost storage options: The scope available via the public cloud gives you more space for the data, using inexpensive object storage tools, and a cloud-based analytics platform can provide thorough integration and visualization for better analysis.
On the less attractive end of the spectrum:
  • Less control: You don't have much visibility into or oversight of the cloud infrastructure, which may not be ideal for your compliance needs.
  • Security challenges: Although most major cloud vendors offer native security features, a public cloud environment will not necessarily be as secure as your private on-premises resources.
  • Vendor lock-in: Relying on a single public CSP makes your business almost symbiotically dependent on that provider. If you decide to change vendors for any reason, the transition can be difficult. This is a key factor behind the rising popularity of multi-cloud.

Private cloud

Organizations that choose a private cloud environment are not without their reasons. Here are some of its potential advantages:

  • Security: Data and apps are either hosted by you, directly on-premises, or through a managed private cloud service from a CSP. Either way, you can make permissions as strict as you want, which can be beneficial for data compliance requirements that demand high security.
  • Low latency: An on-premises cloud will have extremely low latency because the enterprise's resources are all based in the data center, and a managed private cloud offers reduced latency because the resources are used by only one customer.
  • Flexibility: The level of control afforded by a private cloud makes it easy to upscale and downscale as needed.
Nevertheless, there are drawbacks:
  • Cost: The total cost of ownership (TCO) to acquire, set up, and maintain the resources that comprise a private cloud falls entirely on you if it's based on-premises, and it won't be cheap. CSPs offering managed private services will also charge more for the privilege.
  • Scalability issues: Although private cloud gives you the freedom to upscale and downscale as you please, you might be limited in what you can do by your on-premises hardware and resources. VMWare deployments may involve similar limitations.
  • Mobile limitations: Private clouds may have greater security measures in place than their public counterparts, so on-the-go access to private cloud resources could be limited.

5 considerations for selecting the right cloud deployment model

As we said earlier, there's no single right answer regarding whether public or private cloud is your best choice. You need to keep some factors in mind:

  • Security needs: If you're in a highly regulated industry like healthcare or finance, you'll need at least some private resources to complement your public cloud deployment, though a full-fledged private cloud may not be necessary.
  • Growth: Enterprises in periods of rapid growth can benefit significantly from the rapid elasticity and efficiency of the public cloud. Later, they may evolve and use a multi-cloud deployment.
  • Budget: If trying to belt-tighten, or simply control spending, the pay-as-you-go pricing of public cloud may seem particularly attractive.
  • Performance: Private cloud offers very low latency, whereas public cloud performance can suffer under large workloads without proper network management.
  • Resource needs: The biggest public cloud providers are tech giants that offer a broader range of services than their private counterparts. While working with just one presents the risk of vendor lock-in, multi-cloud removes that hazard, and the resources available from public cloud vendors can be valuable for enterprises using the cloud for DevOps. 
Ultimately, the best option may be a hybrid multi-cloud model that leverages the scope of two or more public clouds, while retaining your on-premises infrastructure for the most sensitive data and apps. The tools you use in conjunction with your cloud deployment, such as the leading-edge data analytics engine of Teradata Vantage, should be just as effective in public cloud, hybrid cloud, on-premises, or virtualized environments.