Cloud computing is supposed to make IT more flexible, efficient and easier to manage. But the cloud model threatens to introduce a whole new layer of complexity, unless vendors and industry groups promote interoperability standards that let cloud networks work together.
Vendor competition is a potential impediment, but most major cloud vendors are at least talking about interoperability, including the ability to move workloads from one cloud to another.
"So far, it's closer to lip service, but there are a couple of efforts moving in this direction," says Forrester Research analyst James Staten.
Staten believes the most impressive project is one spearheaded by Distributed Management Task Force (DMTF), which has signed up vendors such as AMD, Cisco, Citrix, EMC, HP, IBM, Intel, Microsoft, Novell, Red Hat, Savvis, Sun Microsystems and VMware for an effort called the Open Cloud Standards Incubator.
The group will let individual vendors demonstrate interoperability between two clouds and document methodologies to ensure that interoperability, according to Staten. The group thus tackles interoperability on a case-by-case basis, but the hope according to Staten is that this process will spur the development of industry-wide standards over time.
Cloud interoperability can mean many things, and users and vendors may not agree on which types of interoperability are most important. But some commonly discussed goals include the following:
- Moving virtual machines and workloads from one cloud compute service to another.
- Single sign-on for users who access multiple cloud services.
- Ability to deploy and provision resources from multiple cloud services with a single management tool.
- Letting one application span multiple cloud services (such as a storage service from one cloud provider and compute capacity from another).
- Allowing data exchange between clouds.
- Letting a private cloud application seamlessly obtain resources from a public cloud when excess capacity is needed.
In more general terms, enterprises want to avoid using a plethora of cloud services with different interfaces, and don't want to be locked in to a particular cloud by technologies that prevent the movement of workloads from one to another.
Amazon has become perhaps the best-known vendor providing both compute and storage services in the cloud model, and the company's APIs have been called "de facto" standards by those who have expressed hope that Amazon will release them as open source software.
Many companies are supporting the Open Cloud Manifesto, which intends to establish a set of core principles that all cloud providers should follow. But notable absences include Amazon and Microsoft.
Several vendors are attempting to tie together different cloud services in ways that make them easier to use for IT shops, but each effort seems to have some limitation.
VMware, for example, is calling its latest virtualisation platform a "cloud operating system" and promising that enterprises can use the software to build private clouds and connect them to public computing resources. But the software only works with hardware that has been virtualised using VMware technology, and the cloud interoperability is only possible if the cloud provider is using VMware. The latter condition eliminates such big players as Amazon and Google.
The Burton Group analyst firm has partnered with vendors to demonstrate single sign-on across real-world applications such as Salesforce.com, Google Apps and Cisco's WebEx, using tools based on standards such as SAML and WS-Federation.
"We're hearing from our clients that many of the applications are moving off premises and into the cloud, and it's putting a strain onto attempts to present as few authentications to users as possible," says Burton Group analyst Gerry Gebel.
Cloud application vendors will have to adopt a standards-based approach to make single sign-on ubiquitous, Gebel says. While he is optimistic that most vendors will come on board, he says the list of vendors following the standards-based approach is probably shorter than the list of those that are not.
In another interoperability effort, the vendor AppZero has created virtual appliances that allow the movement of server-based applications from private data centers to public clouds, and from one cloud to another, such as from Amazon Web Services to GoGrid.
Rival vendor 3Tera says this approach doesn't account for multi-tier applications that span many virtual machines. 3Tera says it encapsulates all the components of an application, including firewall, load balancer, Web and application servers, databases and operating system into one entity that can be easily moved from one cloud to another. But this portability only works if each cloud was built using the 3tera platform.
"The problem right now is there is no interoperability among any clouds," says Bert Armijo, senior vice president of sales and product marketing for 3Tera. Say you write an application specifically for Amazon's Elastic Compute Cloud. Since the code is written specifically for Amazon's platform, "that application is going nowhere," Armijo adds.
Going forward, vendors will have to agree upon a "common set of standards and interfaces" to ensure true interoperability, says IBM cloud computing software chief Kristof Kloeckner.
"In cloud terms, there are some services you receive through a service provider, some services you deliver through an internal cloud, and some that you normally deliver with an internal cloud but you may want overflow capacity for peak times," Kloeckner says. "All this movement of services, applications, and combination of applications only works if all the providers adhere to a common set of standards and interfaces." But today, most public compute clouds are based on virtual machine models that aren't compatible with each other, Kloeckner says.
Mark O'Neill, the CTO of Vordel, says enterprises should be able to use a best-of-breed cloud approach, having applications that span different providers of storage, compute and application hosting platforms.
"Vordel often speaks with customers wishing to make use of best-of-breed cloud services - for example using Amazon for external storage (the S3 service) while using Force.com to pull customer order information into behind-the-firewall applications," says ONeilll. "Key issues are allowing single sign-on across cloud services, for the same application, as well allowing a service running one cloud platform (e.g. a hosted application on Amazon Elastic Compute Cloud) to call a service hosted by another cloud provider (eg Google) in a managed manner."
Vordel's XML Gateway is designed to link single applications to multiple cloud services and provide the single-sign on capability mentioned by O'Neill, all without requiring onerous work on the part of developers.
While Vordel's offering is likely useful for many types of customers, O'Neill says his company hasn't tackled the challenge of trying to move applications from one cloud to another, saying "generally that's an unsolved problem across the board."
But there is room for optimism, says Robert Grossman, chairman of the newly formed Open Cloud Consortium and director of the Laboratory for Advanced Computing (LAC) and the National Center for Data Mining (NCDM) at the University of Illinois at Chicago.
Grossman says enterprises with private clouds should be able to obtain extra computing resources from any public cloud without changing the API. Even today, the open source Eucalyptus private cloud software is largely compatible with the Amazon API, making it easy to get excess capacity from the Amazon cloud, Grossman says. "If I use Eucalyptus in-house and engineer the application correctly, I can get surge capacity form Amazon," he says.
Moving workloads from one public cloud to another is more difficult because that requires standardized management tools, he says. Exchanging data between clouds is another problem. Just as TCP allows the bridging of two networks, Grossman says he'd like to see an inter-cloud protocol allowing multiple clouds to exchange information.
"People are still trying to their hands around some of the issues," Grossman says. "What we have is a very young, very vibrant, rapidly moving industry that is still sort of sorting itself out," Grossman says. "I think things are trending in the right direction."