Rackspace has announced that the customer base for its open cloud is expanding, with "thousands of customers" signing up to both its public and private cloud services each month.

Back in August, Rackspace became the first company to deploy a large-scale open source public cloud powered by OpenStack, with the aim of stealing customers from market incumbent Amazon Web Services (AWS).

The public cloud offering includes servers and databases, but also files object storage with a content delivery network, cloud sites, platform-as-a-service (PaaS) for .NET and PHP, load balancers and monitoring.

Around the same time, Rackspace released its private cloud software known as Alamo, which includes an Ubuntu operating system running a KVM hypervisor. Alamo allows companies to install, test and run OpenStack in a multi-node private cloud environment.

According to Rackspace, organisations are largely adopting its offerings as part of a hybrid cloud strategy. As everything is based on the same OpenStack compute platform, customers can spread applications across their on-premise and public clouds.

In an interview with Techworld, Jim Curry, general manager of Rackspace's Private Cloud business, said that the vast majority of users don't care what the infrastructure looks like, as long as it works.

"Since infrastructure is moving to software, we think you can get that exact same experience running in your data centre," he said.

Curry said that most CIOs love the efficiencies and service model aspect of the public cloud and want to push forward on it very quickly. However, they need to justify the move from a business perspective.

This means proving to the board that the company will not become locked in to a particular service provider, and consequestly putting pressure on service providers to remain as open as possible.

"We want you to choose OpenStack - more than anything else, we want you to make that choice. You don't have to choose Rackspace, you can choose to work with somebody else, but please make sure you understand what they're building to make sure they're not going to lock you in," said Curry.

"We believe that OpenStack users should have the ability to choose from multiple public cloud providers, that they should be able to come and go from Rackspace as they please. Ultimately, the only way that can happen is if consumers actually demand it. I think in this case they are."

Since its release, Rackspace's Private Cloud software has been downloaded by about a third of the Fortune 100 companies, according to Curry, as well as academic institutions, research facilities and thousands of other organisations in more than 125 countries spanning all continents.

To help organisations build expertise in private cloud, Rackspace offers training, certification and support services, as well as advisory guidance to help design a roadmap to the cloud.

"We are first and foremost a hosting company, but what we have learned is one of the ways that we can accelerate the move to the cloud is by helping customers adopt cloud in their data centres," said Curry.

"If you're not running cloud in your data centre today it's very hard to pursue to concept of a hybrid environment where you're running some in the cloud, some not in the cloud. But one of the concepts that people are trying to migrate towards is IT-as-a-service."

The news comes as HP takes the beta label off its own OpenStack-powered public cloud and adds about 50 new applications to its Cloud Maps portfolio of more than 200 apps that are already hosted on HP's cloud ready for "push-button" deployment.

"We see our sweet spot as being a trusted adviser of how to continue to support legacy infrastructure while adding cloud capabilities," said Dan Baignet, senior director of business development for HP Cloud Services.