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Public vs. private: Comparing cloud architectures


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Understanding the differences between public and private cloud computing

Companies considering a public or private cloud computing platform have a lot to consider. This tip can help explain the advantages and disadvantages to each.

This tip is the first in a two-part series on public and private cloud computing. Read part two about the advantages and drawbacks to public cloud services

Private clouds may be a dedicated, or leased, portion of a provider’s hosted facilities. But in most cases, private cloud computing is the conversion of an existing traditional data center into a utility-based computing architecture—you own it, secure it and maintain it just as you always have. The successful move to a cloud is 

hardly quick or simple, and perhaps the biggest challenge faced by IT administrators is choosing between private and public cloud computing architectures. Before picking either option, use this tip to examine the practical limitations and advantages of private cloud computing.

Private cloud computing adoption rates and analysis
It’s no secret that cloud computing has been a misunderstood victim of marketing hype. But regardless of how you define the technologies, it’s clear that both private and public cloud computing is slowly being adopted among modern businesses. According to a recent TechTarget survey, over 15% of more than 1,000 IT respondents indicated that they have implemented some type of cloud, while almost 17% expect to implement some type of cloud computing over the next 12 months.

Private cloud computing shifts the emphasis to computing-on-demand. This generally changes the way that data center hardware is used and shifts the way that departments or stakeholders pay for those computing resources. There are many reasons for organizations to select private clouds. Cost is always an obvious issue, but it’s not necessarily the principal motivator. Organizations that opt for private clouds are usually most concerned with preserving their investment in their existing infrastructures. This was the reason cited by more than 35% of TechTarget survey respondents, and it makes sense for businesses that have already spent significant capital to create their data centers in the first place.

Another 17% said they were motivated by disaster recovery (DR) and business continuity benefits, while 16% said they wanted the security of continued IT ownership. Eleven percent said they sought to leverage the self-service and automation capabilities that are a hallmark of true cloud computing.

Private cloud computing and compliance
Data location may also become a compliance or regulatory issue for private clouds if the organization deploys private clouds across geographic boundaries. It’s extremely difficult to track the physical location of data in a true cloud—as opposed to a virtualized data center—so close attention to regulatory adherence is still required.

Even when an organization deploys a private cloud successfully, making the most of that cloud can be a formidable task. Efficient cloud management involves the establishment of standard operating procedures, a high level of automation, sharing of computing resources between departments or stakeholders, along with a regimented standardization through a single service-level agreement (SLA).

This set of criteria allows an administrator to run the entire pool of cloud resources at an exceptionally high utilization rate and take advantage of significant cost benefits. But these criteria are not normal considerations in a typical data center. “If you don’t have the discipline of the regimented resources, if you don’t have automation to drive this forward, and if you don’t have sharing, you can’t reach that degree of utilization,” said James Staten, vice president and principal analyst at Forrester Research.

Not an all-or-nothing decision
The transition to a private cloud is not an all-or-nothing decision. Experts recommend a gradual transition, starting with a limited cloud infrastructure and running new or low-priority applications on that “mini cloud” within the environment. This cautious approach allows ample time to gain familiarity and comfort with cloud technology and examine the impact of tradeoffs on your particular organization. Success may accelerate subsequent projects, while problems may slow further transition. But a well tested alpha phase of adoption can minimize unnecessary disruption to your business.

Data protection within the private cloud is another important consideration. Organizations that prefer more traditional backup mechanisms can continue to use that approach in the cloud, but the backup tools—such as Backup Exec—must be upgraded to a cloud-compatible version.

Other organizations with more exacting recovery needs may opt for some combination of replication/snapshots and clustering as a means of mixing high-availability and data protection for fast restoration as needed. Perhaps the biggest challenge is disaster recovery (DR). The notion of native DR in a cloud is a misconception, and adopters must pay close attention to the DR plan implemented in their private cloud.

Deploying and testing data protection schemes is another central reason why private cloud computing adoption should be approached gradually.  This approach will leave mission-critical applications with the most stringent data protection requirements until the private cloud is well understood and developed.

A public cloud employs the same basic technologies used to create a private cloud, but public clouds such as Microsoft’s Azure serve a fundamentally different purpose. In virtually all cases, a public cloud is accessed as a service through a provider that hosts all of the hardware, services and applications. Public cloud operation also leverages significant economies of scale, potentially supporting vast server and storage resources spread across numerous geographical areas—even globally.

Efficiency of cloud economics
By its very nature, an efficient cloud is a highly automated and regimented environment that can provide only a fixed set of assets and features to users, Staten said. When organizations try to satisfy the unique needs and wants of every stakeholder, the efficiency of cloud economics is quickly lost.

Not only are assets and features limited in the cloud, but applications are also aggressively removed so that computing resources can be reused as needed. This concept may be hard to grasp for many organizations where applications seem to consume computing resources long after their usefulness is over. “This is a concept that is hard for a lot of enterprises to get, which is why we see so few true private clouds,” Staten said.

Ultimately, experts see many of the biggest cloud concerns easing in the coming years. For example, cloud vendors are actively working to overcome data location worries. As a result, some form of accreditation may eventually identify cloud providers that adopt verifiable data location and protection practices.

The future may yield a broader range of clouds, each providing different sets of assets and catering to more demanding user requirements, Staten said. At the same time, it’s important to remember that neither public nor private clouds will handle every computing need. Traditional data centers will continue well into the future—even as the clouds move in.

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