Just when you thought you were starting to understand cloud computing, and private cloud computing, here comes hybrid cloud!
Vendors are already flocking to the term – it means everything from remotely managed appliances to a mix of virtual and non-virtual servers to traditional applications using cloud services, and everything in between. So what is it?
Gartner defines a hybrid cloud service as a cloud computing service that is composed of some combination of private, public and community cloud services, from different service providers. A hybrid cloud service crosses isolation and provider boundaries so that it can't be simply put in one category of private, public, or community cloud service.
This definition is intentionally loose, because there really are a lot of interesting edge exceptions, and rather than draw a tight boundary around what is, and what isn't, this seems to get to the central point of the matter well enough.
So why is hybrid cloud computing useful? It allows you to extend either the capacity or thecapability of a cloud service, by aggregation, integration or customization with another cloud service. For example, there might be a community cloud service that needs to include data from public cloud services in its analysis – while retaining a certain amount of analytics or data privately.
Or a private cloud service that needs to expand its capacity by extending temporarily into a public cloud service (or perhaps a somewhat private cloud service offered by a third party provider). It allows you to balance your privacy needs with additional capacity and capability needs.
The terms "overdrafting" and "cloudbursting" have been used to describe how a hybrid cloud service could be used for capacity, but they paint an extreme example. Hybrid cloud compositions can be static (designed to require multiple services), composed at deployment/usage time (e.g., perhaps choosing one service provider or another, or combining based on policies), or composed dynamically (e.g., cloudbursting – or perhaps at disaster recovery time).
While these compositions can be designed into services and/or cloud-based applications, they will often be managed by cloud services brokerages – the intermediary that Gartner expects to become a major phenom in the next few years (something like the system integrator of the cloud world). Large enterprises will often take on this role themselves – in fact, this is central to Gartner's vision for the future of IT.
So what does all this mean now? It means look out – the world is not going to be neatly divided into separate private and public cloud services. To maximize efficiency and take advantage of publicly available cloud services, we're going to munge them together. Private clouds, in particular, will not stay simply "private" for long – Gartner expects most private cloud services to become hybrid. Minding the gap is key – planning for it, balancing isolation and value, leveraging it – hybrid will move from the realm of hype and vendor cloud-washing to reality in the next few years.