Hosting company Rackspace has launched a private cloud offering, the move follows its public cloud launch in May and is aimed at larger enterprises who are looking to take advantage of the cloud.

John Engates, Rackspaces's CTO said that most of the large organisations were following the line taken by the likes of VMware and Cisco and are looking at the private cloud. "We take the concept of private cloud and develop it further," said Engates. "These companies want all the benefits of owning their own infrastructure but see the advantages of hosting it within Rackspace's data centre to gain from Rackspace's investment in its own infrastructure."

He cited various advantages for business to adopt Rackspace's private cloud. "We've used VMware technology as many of the larger customers have already made an investment in that virtualisation technology and they want a seamless path between existing deployments." But other factors came into play too. "These businesses want the security that we can offer. They have various compliance requirements - in the US, they have to conform to Sarbanes Oxley, if they're in finance they have to adhere to PCI constraints," he said.

Businesses outside the US, who have their own issues with privacy (such as those inside the EU) would not find their data being sent abroad, said Engates. "Businesses in the UK, for example, will find their data being held in our data centres in London or Slough," he added.

The decision to build the private cloud on top of VMware is in a stark contrast to Rackspace's use of XenServer as the platform for its public cloud. "There are some issues between migrating between the two platforms," said Engates, explaining that was the issues that Rackspace still had to deal with. However, he said, there were very good reasons for building the two systems on different platforms.

"Some of it is just to do with the cost, we're using open-source Xen as we wanted to be competitive with the likes of Amazon." But, he explained, there were cultural factors too. "In the public space they're less aware of what's behind the cloud. On the private side, customers are much more aware of what's available and want that seamless transition to VMware, " although, he stressed, the private cloud offering wasn't reserved solely for VMware customers.

Engates added that it was impossible to compare Rackspace's Prviate Cloud with its public cloud offering."With the public cloud, there's nothing to setup, you connect and you're away , you can pay by minutes or by the hour . Private Cloud is different, there's stuff that has to be there the whole time. For example, firewalls and load-balancer s, only the virtual machines on top are ephemeral. We've specced out a typical example that enterprise customers might have to pay and that's $6,000. That includes the underlying infrastructure as well as eight virtual machines."

However, Engates said there was some flexibility in the pricing for Private Cloud - "people only pay for machines that are turned on and used. So, for example, it could be attractive to an enterprise that has large-scale batch processing to do at the end of the month,"

Future plans for Private Cloud include autoscaling where servers can automatically cope with increased workload without being pre-provisioned. "We're working on this," said Engates. "To a large degree we're dependent on what VMware does here with vCloud and vSpehere. VMware has some work to do to develop some APIs to enable this. We have auto-scaling in our public cloud but not private as yet = although we are already We are testing early releases of the software."