"However, no outside firm has inspected or audited Amazon's data centers to verify these claims," Reeves writes. "Due to lack of available information and audited inspection regarding Amazon's data centers, Burton Group cannot verify Amazon's availability claims."

Specifically, Burton Group says Amazon customers have no way of determining the "physical redundancy level and data protection" of physical components such as servers, storage devices, network and power infrastructure. Burton Group also faulted Amazon for replication rates in its Simple Storage Service and a lack of failover between data center regions.

Amazon spokeswoman Kay Kinton said the Burton Group report contains inaccurate statements. For example, the report says Amazon lacks , when in fact Amazon does have that certification, Kinton writes in an e-mail to Network World.

"In terms of reliability, we often hear from our customers that AWS [Amazon Web Services] can achieve higher degrees of than they've been able to achieve on their own," Kinton writes. "Additionally, AWS gives users a great deal of control and visibility into a user's environment. Users can choose where to place their data, they can run their applications and back up to multiple availability zones and in the event of any service interruptions, they have access to a service health dashboard that gives regular updates on the service health. We also have features that provide monitoring, Auto Scaling and Elastic Load Balancing for even greater resilience in building applications. One of the main reasons customers use our services is the reliability that we're able to provide."

Kinton also noted that Amazon recently launched the Amazon Virtual Private Cloud (VPC), which connects a customer's existing infrastructure to a set of isolated cloud computing resources with a VPN connection.