Typical apps deployed using open-source frameworks include Web and social applications, as well as mobile or customer-facing websites, says Jerry Chen, vice president of cloud and application services at Cloud Foundry. Such frameworks are also useful when organizations need to deploy applications quickly and scale them up and down as needed.
Legacy applications requiring hardware or software that may not be supported on the Web tend to be less attractive candidates. "While it is very possible to migrate many data center applications from local servers onto [virtual] cloud-based ones, the ROI is not always clear," says Bill Weinberg, senior director of Olliance Group at software and services provider Black Duck Software. "The downside can lie in potential security issues, divergent response to loading, throughput bottlenecks and availability."
OpenStack and Cloudscale are better choices for complex applications than Eucalyptus, says Nataraj, because they do a better job of hiding the complexity of networking. For an application that, for example, requires a user "to connect from a different IP range," a customer would "have to write custom code to make that happen with Eucalyptus," he says. With OpenStack, the "switches" required to make those new network connections are already present.
The number and quality of developers involved in an open-source project can also be a good indication of the project's quality, many observers say. If developers from several companies are involved, vendor lock-in is less likely to be a problem, says Nataraj.
Roby, however, suggests focusing on a commercial vendor's level of commitment, rather than that of the community. "It's largely a myth that there's a lot of new code being developed by a large group of people," he says. "Any of these successful products are developed by a small group of people," with the community at large "providing feedback and maybe doing testing or providing documentation."
Miles also warns of "token" open-source efforts by partnerships among major vendors. "If both those companies don't really rely on the product for revenue, at any point in time either or both will just walk away, and the product will die," he warns.
The unconventional licensing terms that some open-source developers impose on their software, such as one requiring that "the Software shall be used for Good, not Evil," raise eyebrows in corporate legal departments. Posing a more serious problem are licenses that require a company to share any enhancements with other members of the community -- which creates the possibility that the company may have to reveal "best practices" to competitors.