Engine Yard, the San Francisco-based cloud for Ruby language applications, has launched xCloud, a second platform as a service for Ruby on Rails developers. In effect, it's giving developers a choice between infrastructure supplied by Amazon's Elastic Compute Cloud or Terremark's Enterprise Cloud.

It previously gave Ruby developers only the option of launched their applications on the EngineYard AppCloud platform, a front end to Amazon's EC2.

The xCloud gives Ruby developers using Terremark high-performance SAN storage, guaranteed resources, custom hardware support and guarantees of compliance with Payment Card Industry (PCI) security standard, health care's HIPAA standard, and the Service Organization Auditing Standards or SAS70, said Tom Mornini, Engine Yard CTO, in the announcement.

"We created xCloud in response to growing demand from customers who require strict regulatory compliance and low-latency, high-throughput disk I/O for superior database performance," Mornini said. He is a co-founder of Engine Yard. "Terremark's infrastructure offers unique benefits, which we will pass along to our customers," said Abheek Anand, product manager for Engine Yard, in an interview. Terremark offers enterprise workload service level agreements on performance and availability. If a Ruby application running on Terremark's cloud failed to deliver, Terremark guarantees that it has an auditable infrastructure that could determine whether the problem lay with its servers or with an external network. That kind of assurance allows Ruby business application suppliers to make more guarantees to their own customers.

In addition, there's another major difference between Terremark and Amazon Web Services' EC2. Terremark runs part of its server infrastructure in Miami on VMware's vCloud Express, meaning it is ready to run VMware's ESX Server virtual machines. ESX uses VMware's VMHD virtual machine format, so workloads can be sent to Terremark in the same format as they currently exist in VMware customers' sites. EC2 runs Amazon's own Amazon Machine Image or AMI format, which can be built from ESX virtual machines but the end user needs special tools and know-how.

If you're already running Microsoft Exchange as a VMware virtual machine, you can move that virtual machine into the Terremark's cloud if you choose to without too much difficulty, said Anand. Likewise, you can build new applications in Ruby on Rails and run them as VMware virtual machines on Engine Yard's xCloud, with Engine Yard supplying needed middleware and adjustments to make them run effectively, he said. In many cases, "customers don't care what the underlying virtual machine infrastructure of the cloud is. They want us to handle that for them," said Anand.

The biggest advantage of offering a second cloud infrastructure platform, he said, lies in "the idea of getting guaranteed resources" in storage and networking as well as virtual servers.

Engine Yard is three-years old and has 1,250 customers. Ruby on Rails is a popular scripting language framework that lends itself to rapid application development. There are an estimated four million Ruby developers worldwide, Anand said.