A few years ago, the IT world was focused on public cloud computing. In 2010, after IT directors expressed concerns over public cloud security issues, the focus shifted to private clouds. And now, because everyone wants operational flexibility, hybrid clouds are at the top of the wish list.
Several recent cloud surveys confirm these high levels of interest in hybrid cloud. A Unisys survey in January 2011 indicated that 21% of IT organizations are focusing on hybrid clouds, and a 2010 Sand Hill Group survey of over 500 IT managers indicates that hybrid cloud use will triple over the next three years.
Examining hybrid cloud architecture
So what is a hybrid cloud? For starters, it is a composition of at least one private cloud and at least one public cloud. The private cloud can be an on-premises private cloud or a virtual private cloud located outside the enterprise data center. In the illustration below, we provide one of the simplest macro views of a hybrid cloud — a single on-premises private cloud and a single off-premises public cloud:
The black circles in the illustration represent active virtual server images and the white circles represent virtual server images that have been migrated (using safe connections). The arrows indicate the direction of migration. Enterprise users are connected to the clouds using safe connections, which can be virtual private networks (VPNs) or secure HTTP browsers.
A hybrid cloud could also theoretically consist of multiple private and/or public clouds. The enterprise data center denoted in the illustration may have active servers (virtualized or physical) that are not included in the private cloud.
What is driving hybrid cloud computing?
Hybrid cloud interest is powered by the desire to take advantage of public and private cloud benefits in a seamless manner. Some of the risks associated with public and private clouds, however, can also be issues in hybrid clouds. The benefits and risks of public, private, and hybrid clouds include:
Public cloud benefits:
o Low investment hurdle: pay for what you use
o Good test/development environment for applications that scale to many servers
Public cloud risks:
o Security concerns: multi-tenancy and transfers over the Internet
o IT organization may react negatively to loss of control over data center function
Private cloud benefits:
o Fewer security concerns as existing data center security stays in place
o IT organization retains control over data center
Private cloud risks:
o High investment hurdle in private cloud implementation, along with purchases of new hardware and software
o New operational processes are required; old processes not all suitable for private cloud
Hybrid cloud benefits
o Operational flexibility: run mission critical on private cloud, dev/test on public cloud
o Scalability: run peak and bursty workloads on the public cloud
Hybrid cloud risks:
o Hybrid clouds are still being developed; not many in real use
o Control of security between private and public clouds; some of same concerns as in public cloud
Addressing the hybrid cloud challenge
The challenge of hybrid computing is to provide seamless operation across platforms, cloud application programming interfaces (APIs) and hypervisors. Users prefer to use their data center tools to manage hybrid cloud environments. Ideally, they want to be able to create applications, or move existing applications between the clouds in a hybrid cloud environment, without having to change anything serious like networking, security policies, operational processes or management/monitoring tools. This is a problem because, due to issues around interoperability, mobility and differing APIs, tools, policies and processes, hybrid clouds generally increase complexity.
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