Often, in planning for cloud services, people prefer to first build and launch "greenfield" applications, versus making attempts to virtualize, abstract, transform, replace, transition, or upgrade (pick your term) an existing application/system. It makes sense, since no one wants to mess with an application and leave end-users waiting for days or weeks until things are ready to go again on a new platform. However, even greenfield deployments may not be as pristine as perceived.
Edward Haletky, for one, says there's really no such thing as a greenfield project, unless you are starting a company from scratch. In a recent post at The Virtualization Practice, Haletky, president of AstroArch Consulting and author of two books on VMware enterprise virtualization, argues that even when launching new applications or services that never existed before, there are still integration issues that need to be considered. "What is defined as greenfield is really just a grain of sand on an island of technology that still needs to integrate into the greater organization," he points out.
Any new application or service still must be configured and integrated into the existing infrastructure, he points out. "Anything that is placed into that environment must work within the virtual environment or the existing cloud environment, whether the item placed there is a security device, converged infrastructure, storage, management tool, performance tool, or even a new hypervisor. These must all integrate into an existing deployment."
The bottom line is more information and transparency is needed. Any and all new services and applications need to fit into an existing data center infrastructure, and may even require changes to underlying services or tools, Haletky points out. Vendors need to provide more support in this regard as well, with integration instruction and assistance, as well as reference archtectures, he says. "Vendors can reuse existing architectures, but they should tell us how they differ from past products and what hardware is required to make them work."
So, there are actually no greenfields -- only new applications or services that need to be compliant with existing and tested infrastructure and technology to make things run as they should.