Organizations trying to decide between virtual private cloud vs. private cloud must first define what they want to accomplish. A private cloud gives individual business units more control over the IT resources allocated to them, whereas a virtual private cloud offers organizations a different level of isolation.
Virtual private clouds are typically layers of isolation within public clouds, but they might lack the self-service portal that enables IT to provide individual business units with DIY IT environments. Private clouds are generally on-premises environments with self-service portals that designated employees can use to deploy resources without intervention from IT.
But interest in the private cloud is about much more than just technology; private clouds represent a fundamental shift in the way organizations deliver IT resources.
In the past, corporate IT acted as a gatekeeper for all things tech. If a business unit within an organization needed to deploy a new application or a new service, they went through IT.
This way of doing things was problematic for both the business units and for IT. Whenever a department had to seek IT approval for a tech project, it ran the risk of IT denying the project or modifying its scope beyond recognition. Even if it was approved, the business unit might have to wait weeks or even months for IT to implement it.
The old way of doing things was also problematic for the IT department because it often put IT in the awkward position of having to say no to someone else's ideas. On the other hand, if IT did approve the project, it meant an increased workload for the IT staff that had to deploy, maintain and support the new application.
Moving away from traditional virtual infrastructures
Private cloud environments represent a shift away from the rigid administrative model that organizations have used for so long. Rather than the IT department acting as the sole governing body for all the organization's tech resources, it instead takes on the role of a service provider.
In a private cloud, the IT infrastructure is carved up into a series of private areas, and each area is assigned to a specific business unit. One or more designated employees within the department take on the role of tenant administrators for the available resources. These administrators are free to use the resources as they see fit without first seeking IT approval.
This doesn't mean that tenant administrators have total autonomy, nor does it mean that they require specialized IT skills. Every organization sets up its private cloud differently, but IT usually provides tenant administrators with a self-service portal that is designed to simplify tasks, such as deploying and managing VMs. Furthermore, IT usually creates VM templates that tenant administrators can use any time they create a new VM.
In other words, tenant administrators can create VMs on an as-needed basis, but must do so within the limits IT has put in place. These limits ensure that tenant administrators don't deplete the underlying infrastructure of hardware resources. Additionally, the use of templates guarantees that admins create VMs in accordance with the organization's security policies.
Virtual private cloud vs. private cloud
When it comes to virtual private cloud vs. private cloud, the terms are sometimes used interchangeably. In most cases, however, a virtual private cloud is different from a private cloud.
In a private cloud model, the IT department acts as a service provider and the individual business units act as tenants. In a virtual private cloud model, a public cloud provider acts as the service provider and the cloud's subscribers are the tenants. Just as the tenant administrators in a private cloud are free to create resources within the limits that have been set up for them, a public cloud's subscribers are also free to create resources within the public cloud.
When public cloud subscribers create resources, such as VM instances, databases or gateways, those instances are created within a virtual private cloud. Think of the virtual private cloud as an isolation boundary that keeps subscribers from being able to access -- or interfere with -- each other's resources.
Each public cloud provider has its own way of doing things, but some providers allow tenants to define additional virtual private clouds. For example, Amazon allows AWS subscribers to create as many virtual private clouds as they need.
Each virtual private cloud acts as an isolated environment. Organizations sometimes use virtual private clouds to isolate web servers from other cloud-hosted resources, or to create an isolation boundary around the virtual servers that make up a multi-tier application.
The new norm: Organizations don't have to choose
In spite of virtual private cloud vs. private cloud distinctions, the lines between them are blurring more than ever. Rather than choosing between a private cloud and a public cloud, most organizations opt for a hybrid cloud.
Admins can construct hybrid clouds in many different ways, but one option is to create a self-service environment similar to that of a typical private cloud, but to configure it so some resources reside on premises, while others reside in the public cloud.
Startups will almost always benefit from operating entirely in the public cloud because doing so enables them to avoid a large upfront investment in IT infrastructure. For organizations that already have an on-premises IT infrastructure in place, however, a hybrid cloud usually offers the best of both worlds.