Managed hosting provider Savvis has rolled out a service that allows (ISVs) independent software vendors to offer their applications in a software-as-a-service model.

The service allows ISVs to take a single-tenant application and offer it as a hosted service to multiple clients through Savvis' 29 data centers around the world, said Chief Technology Officer Bryan Doerr. It is available first in the U.S. and the U.K. and will be offered worldwide by the end of the year, he said.

Savvis partnered with Parallels to use its Virtuozzo Containers virtualization software to offer the service. The product divides a server OS into individual containers, each of which is assigned to an ISV customer and hosts multiple instances of its application. Customers also use Parallels' Automation software for provisioning accounts, billing and linking to payment systems.

More and more end customers are turning to SaaS (software-as-a-service) to reduce costs, putting pressure on ISVs to offer their applications as services. CRM (customer relationship management) has seen the widest uptake, with 15 percent of software revenue in 2007 coming from SaaS applications, according to Gartner. The fastest growing segments are for office suites and digital content creation tools, where SaaS revenue will roughly double on average each year from 2007 to 2011, Gartner said.

Some ISVs have developed multitenant versions of their applications, which allows multiple end users to access a single instance of their software. Savvis hosts applications for some of those vendors, but the new service is for ISVs that have yet to develop multitenant products. They don't need to rewrite applications to use the service, according to Doerr, and need only to bring it in and test it in the SaaS environment.

"We think of this as a transition period. We think ISVs will use this [service] as a quick go-to-market and eventually rewrite their application to be natively multitenant," Doerr said.

The infrastructure services, which also include application firewalling, are the first in a series of SaaS offerings that Savvis will roll out in the coming months. It also plans "lifecycle services" such as virtual labs hosting, where clients can develop and test applications, and application performance monitoring.

Longer term it will offer "marketplace" services that encourage ISVs to link their applications with those of other Savvis hosting customers. One ISV might offer a load testing service that other ISVs can use, for example, or a CRM provider might integrate its service with another ISV's human resources application.