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Comparing private cloud vs. public cloud application support

Private cloud computing holds a strong appeal to businesses that are leery of public cloud providers’ ability to support their applications. In some cases, such as minimizing latency, this wariness may ring true; in others, as IT pros often say, it depends.

Private cloud seems like the obvious next step for businesses with in-house data centers, because it enables managing hardware locally -- the traditional IT path -- while letting end users access infrastructure remotely, which has become the norm today. Yet, does that control come with too many limitations? Does public clouds’ broader application support services balance out minor losses in control? Cloud experts explore how private cloud vs. public clouds stack up in key application support criteria -- scalability, workflow, device support and more.

Is your IT in the 8%?

Comparing on-premise systems application support capabilities to a prospective public cloud provider’s system is the first between private cloud vs. public cloud.

“Can your systems maintain application support in all situations at the same level of rigor that the hardware and software in the public cloud?” asked Dan Cornell, principal for The Denim Group software consultancy. If so, then that’s one mark in the pro column for private cloud. “Having my apps on a server where no other organizations reside is far preferable,” he said.

Don’t wear rose-colored glasses when reviewing in-house application support capabilities, said James Staten, principal analyst, Forrester Research Infrastructure and Operations. Approximately 8% of enterprises have the operational capability to run and maintain a private cloud, according to Forrester’s research.

That 8%, however, will build a strong, niche base of private cloud instances, making up $15.9 billion of the $241 billion cloud computing market predicted for 2020 by Forrester. Public cloud will account for $159.3 billion, with the rest split between hybrid cloud.

Application reach

Is the application you're planning to deploy one that you want to have globally available, and will it have the need to be globally available with high-performance and with dynamic activity? If so, private cloud may not be your best option, cloud experts say.

You're going to get better economics on a public cloud with any application that scales out,” said Staten. “If your application has that behavior, it is going to activate public cloud economics and by default be cheaper there.”

Private cloud environments can get better scalability if user – employee, customer, supplier, etc. -- access is increased, according to Bill Claybrook, president of New River Marketing Research, a cloud, open source and virtualization analysis firm.

“If the apps are bursty, requiring additional resources at scheduled or unscheduled times, then the private cloud would have to have resource overcapacity to handle the scaling,” Claybrook said. Yet, providing access to many non-employees can be costly technology-wise and risky security-wise.

A deciding factor is whether a public cloud provider will commit to a service-level agreement (SLA) that would guarantee the high-performance required, said Claybrook. Also, he recommends making sure the public cloud vendor has the server clout to handle high-performance apps, which usually requires high-octane servers with price tags of $20,000 or more each.

Application complexity and latency

The complexity of your application and whether it has latency dependencies are important considerations when choosing between public and private cloud.

Can you use a SaaS application as it is designed? A key decision point is how much you can consume the SaaS app versus how much you have to change it to make it fit your company’s needs, according to Staten. If your application is more complex than the SaaS app and you have to do a lot of customization, it will absolutely be more expensive to use SaaS than a private cloud.

Surprisingly, the location of a public cloud vendor’s data center plays a role in application support, too. Complex applications also may require some application elements to be on-premise or to have their own dedicated hardware. Public clouds typically don't give you dedicated hardware, said Staten. They may have an ancillary service that does, however. For example, a public cloud service provider may have cloud and a traditional hosting, as well as co-location, in the same data center.

Private cloud may be preferable if your application has to communicate with other applications in its workflow and must resolve the connections between all those different applications in milliseconds, Staten said. Public cloud providers may not co-locate all of those interconnected applications on the exact same hardware.

Frequently, public cloud providers spread applications across the dynamic environment to whatever capacity and resources are available, which could make latency a big issue. “Very few cloud providers today can deliver the needed quality of service for networks,” he said.

Latency is less of an issue in the U.S., where most public cloud providers reside. The farther away the apps and data are, the larger the latency, said Claybrook. Data is accessed over the Internet unless the enterprise (private cloud) or public cloud provider is willing to pay for a faster, dedicated network for moving data, expect latency. Public cloud users should address potential latency problem in SLAs. Also, check out how much extra cloud providers charge for network bandwidth. If your company needs strict control of latency, then consider private cloud.   

Technology adoption issues

The more adoption of new technologies you have to do, the more expensive it will be to use a private cloud, experts say. In particular, today the speed of adoption of consumer-like devices in enterprises increases the importance of how quickly you can move to support a device.

For example, it almost always takes less time and money to add support for a new device on SaaS than on private cloud, said Carl Brooks, analyst, 451 Research Infrastructure Services. With a private cloud, you have to upgrade the hardware, think through the architecture, determine how many users there will be and consider the implications of all of that and more. What can take internal IT months can be done on a SaaS cloud in weeks.

Let the cloud computing buyer beware

Do your own analysis of how cloud computing options fit your application support needs, and don’t be swayed by public cloud success stories or vendors’ pitches, experts say. Also, said Staten, don’t jump to the conclusion that public clouds are the best choice for large applications. “Size is irrelevant,” he said. Instead, look to how well your application activates cloud economics. 


This was first published in May 2012

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