Public Cloud Vs. Private Cloud: Which Side Are You On?

The battle is raging, but peace may soon be at hand. Is one cloud better than the other, what’s the difference, and can you have the best of both worlds?

Cloud computing (a.k.a. grid or utility computing) has matured to the point where most organizations are currently in the cloud to some degree or are contemplating making the move. The benefits in terms of savings (fewer hardware and software investments), scalability, and agility are well documented. So the decision to head for the cloud is virtually a no-brainer — especially for companies that don’t already have enterprise-level datacenters with the requisite compute, storage, networking, and operating system resources. Deciding what kind of cloud, however, requires a bit more brainpower.

The Public Cloud

The public cloud provides commercial services like Google Apps, storage, sales force automation, and other suitable Software-as-a-Service (SaaS) applications over the Internet in real time. By sharing IT infrastructure with others and benefiting from the flexible distribution of resources, companies realize significant savings and faster time-to-market for deploying new services and bringing proprietary apps online. The downside? By throwing in with the public cloud, you have less control. Which is why some IT managers are looking to bring the benefits of an external cloud in-house by delivering metered services exclusively via internal resources.

The Private Cloud

A private cloud takes all the upside of its public counterpart and parks it inside the corporate data center. According to Wikipedia, it "emulates cloud computing on private networks…and offers the ability to host applications or virtual machines in a company’s own set of hosts." A private cloud provides "the benefits of utility computing — shared hardware costs, the ability to recover from failure, and the ability to scale up or down depending upon demand." The key technologies required are virtualization for scalability, flexibility, and maximum hardware utilization; automation for fluid workload provisioning; and, authentication to restrict unauthorized access. But unlike with a public cloud, you have to build and manage the infrastructure yourself, and thus, won’t see the upfront savings on capital outlays and management expenses that come with a publicly shared resource pool. Since the economy has been a key driver behind the attraction of cloud computing, why would you want to bring the cloud inside?

Why Go Private?

The primary reasons are security and control. For starters, in a public cloud, you effectively put all your eggs in one basket. If the cloud goes down or the vendor goes out of business, you’re out of luck. With a private cloud, you provision your own services and control access via an in-house Web portal.

By keeping data within the data center, you eliminate out-migration costs, gain direct control over Service Level Agreements (SLA), and enable better compliance with a variety of regulations surrounding data privacy, protection, and storage. In fact, some government regulations and corporate governance mandates dictate that certain types of customer data must reside on premises, making the use of a public cloud unfit for some applications.

So Where’s It All Heading?

Analysts say that organizations with enterprise budgets and deep staffing will increasingly use private clouds for delivering mission-critical business apps and hosting development and test sites — particularly if they already have major investments place. An additional application that is showing great promise is the use of "partner" clouds as self-service Web portals for customers and partners. While organizations are not likely to move their entire IT infrastructure to a private cloud, it’s clear that the provisioning of commodity services across shared, virtual resources can have a major impact on the bottom line: lower costs, less management burden. One caveat, though — to be cost-effective, a private cloud needs to draw enough workload to justify the investment. Without sufficient volume, it will not benefit from the economies of scale inherent in cloud computing.

The Best of Both Worlds

Given their many positives, it’s not surprising that private clouds have become very appealing. A recent IDC survey revealed that 55 percent of IT executives said they’d prefer using a private cloud over a public offering — but not for all applications. The lines between the two are blurring and as luck would have it, a public-private hybrid model is a hot, new trend. Mike Vizard of IT Business Edge notes in his blog that "cloud computing will routinely become more hybrid with application workloads dynamically shifting back and forth between internal and external clouds. Once that happens, however, the distinction between public and private cloud infrastructure will start to fall apart and the term cloud computing itself may simply disappear…" To hasten that development, new technologies that let you build virtual private clouds on top of public infrastructure are emerging. Just this February VMware introduced a connector for moving virtual workloads between VMware-based private clouds and publicly hosted cloud services. "The software makes it as easy as possible for VMware customers to extend their datacenters into the cloud," said Matthew Lodge, VMware senior director of cloud services. It appears that maybe you can have it all.

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