Hosting providers offering virtual servers could be barking up the wrong tree, according to Rackspace. Virtualisation is not yet ready for the big time, and is unlikely to save its users money, the hosting company claimed.

The claims followed a survey, in which 87 percent of 3000 Rackspace customers said they would not share a server with other hosting customers. Asked whether virtualisation is ready for mission-critical applications, more than a quarter said it was not.

This suggests that virtual servers have only limited application within the hosting business, and that companies who already offer virtual hosting have jumped the gun, said Nicholas Keller, Rackspace's platform products director.

He added that the customers cited security and performance as their top concerns, and said he half-agreed with them.

"We believe we have the right technology, people and processes to mitigate the security risk," he said. "But on performance, we agree with our customers - the technology is still maturing."

In particular, he claimed that today's hypervisors don't have the technology to traffic-shape their network usage, so having several VMs contending for the same heavily-used network connection can be a problem.

However, he said that Rackspace still plans to offer virtual servers, using VMware. It will do so on the basis that the customer buys a physical machine which is then partitioned into multiple virtual servers, all for that customer to use.

"We are part of the VMware service provider programme, and have been for eight to 10 months," Keller noted. "The reason we are a bit behind the curve is first, we wanted to truly understand our customers' needs here, and second, we believe any system offering is only as good as the management layer that sits above it."

He said that customers choosing a virtualised approach should not expect it to save them much money, as the same systems management overhead will be the same - and possibly higher.

Instead, he said they should look to it for increased flexibility and scalability, as it makes it simpler to move resources around to meet demand, and for the ability to take system snapshots, for example to quickly roll back a faulty software patch or fix.

And he warned that anyone taking the virtual route must pay extra attention to sizing the physical server. "That's something that's often overlooked, with the result that people overload the machine doing consolidation," he said.