While much of the industry focus surrounding cloud computing has been on the giants in the public cloud space , companies like Amazon Web Services, Microsoft, and Google, for instance, many enterprises are eschewing these options for production workloads and instead building private clouds. But that raises the question, just what is a private cloud? And what distinguishes a private cloud from both public clouds and traditional IT as we practiced it before cloud computing arrived on the scene? Indeed, as recently as 2009, Werner Vogels, CTO of Amazon Web Services, was claiming that a “private cloud is not the cloud.” Is that true? If not, why not?
What is Privacy?
First, we need to understand privacy a bit more. In what sense is a private cloud private? There are a few ways we might be tempted to answer that question:
- A cloud might be private in the sense that it exists behind a security perimeter (e.g., firewall) and is only accessible from the public Internet through very carefully controlled means. Here, privacy means, “Not visible to the public Internet.”
- A cloud might be private if it runs only workloads from a single organization. Whereas a public cloud might place workloads from different companies in such a manner that they would share infrastructure, a private cloud would eliminate this possibility. In this case, privacy means “not shared outside the organization.”
- A cloud might be private if the organization that owns the infrastructure is also the one that owns the workloads running on top of it. In this sense, privacy means “everything is owned by the same organization.”
Private cloud. The cloud infrastructure is provisioned for exclusive use by a single organization comprising multiple consumers (e.g., business units). It may be owned, managed, and operated by the organization, a third party, or some combination of them, and it may exist on or off premises.
Many people think private clouds are always operated by the enterprise and must reside in the enterprise data center, but that’s not the case. An enterprise, could, for instance, hire a consulting services company (e.g., CloudOps or Mirantis) to build and run a cloud in a service provider colo facility (e.g., Savvis, Switch, or Terremark), using leased or rented computers and storage. Any and every permutation is fair game, as long as the infrastructure is provisioned for the exclusive use of a single enterprise.
Private Cloud Types
The NIST definition for private clouds doesn’t mention anything about the which types of cloud (IaaS, PaaS, or SaaS) are applicable to private clouds. In fact they are all applicable:
- IaaS — Many enterprises will build an initial public cloud by evolving from a basic server virtualization environment. What’s the difference between these? Fundamentally, it relates to how the cloud is exposed to users. NIST defines five essential characteristics of clouds: on-demand self-service, broad network access, resource pooling, rapid elasticity, and measured service. A virtualization environment will deliver or or two of these (namely resource pooling), but not the others.
- PaaS — Some enterprises will build standard enterprise PaaS environments, providing more than simple operating system instances on demand. We’ve covered JP Morgan Chase’s efforts at rolling out a private PaaS environment before. Sometimes, enterprises will build this themselves, creating a custom environment with a specific set of components, many of which might support legacy applications and interfaces. Other times, enterprises will rely on external vendors like Apprenda or Cloud Foundry.
- SaaS — This is a bit of an odd one. Some people have argued that there’s little difference between private PaaS and enterprise IT running software as we always knew it. But SaaS has a distinct billing aspect to it, and private SaaS will differ from old IT running software precisely in that it provides a more accurate accounting system for performing enterprise-wide charge-back or show-back.
- Others — While all private clouds will fit into one of these three types, there are going to be specializations that might deserve their own names. Some enterprises, for instance, are having great success in running Database-as-a-Service private clouds, often based on clustered, highly available versions of Oracle or other databases.
Why Build a Private Cloud?
For all of Werner Vogels’ statements against private clouds, almost every large enterprise I have talked to is starting their production cloud journey with a private cloud project instead of public clouds (though, to be clear, many are running PoCs and lab experiments with public clouds). The obvious question is why?
- Security risk — Whenever anybody polls enterprises and asks them about reasons for not moving to cloud computing, security is inevitably the #1 answer. Enterprises have a responsibility to customers, employees, and shareholders to ensure that confidential information is not compromised. Public clouds are perceived as an increased security risk. While there is evidence that suggests that public clouds are actually more secure, they do represent a major change in the IT landscape, and it’s prudent for companies to move carefully.
- Project risk — Many companies already have an existing server virtualization environment. Given existing capital equipment and software infrastructure, it makes sense to try to reuse that by evolving the virtualization environment into a full-fledged private cloud, reducing project execution risk by eliminating some variables from the equation.
- Cost — Early in the cloud era, pundits would claim that public clouds would be cheaper than traditional IT because the large public cloud providers could “buy in volume and operate at scale,” gaining enormous efficiencies over the regular enterprise IT organization. That’s certainly true for small and mid-sized companies that could never afford to build a highly available, tier 4 data center with a state of the art cloud inside. But many larger organizations already have such facilities, buy large quantities of servers and storage already, and have top-notch operations personnel on staff to run everything. Having done the analysis, many large enterprises are saying that they can operate a private cloud for as little or even less than the large public providers like Amazon, particularly for long-running workloads. Leverhawk will be publishing more about private cloud economics in future articles.
Many enterprises are starting their cloud journey with a private cloud, reducing risk and gaining some experience before they use public clouds. Private clouds come in all flavors, IaaS, PaaS, and SaaS. They can be owned and run in your own enterprise data center or located in a 3rd party data center and run by external operations companies. The prime characteristic of a private cloud is that it contains workloads from a single organization.