  The ATLAS Google Project was established as part of an ongoing evaluation of
the use of commercial clouds by the ATLAS Collaboration, in anticipation of the
potential future adoption of such resources by WLCG grid sites to fulfil or
complement their computing pledges. Seamless integration of Google cloud
resources into the worldwide ATLAS distributed computing infrastructure was
achieved at large scale and for an extended period of time, and hence cloud
resources are shown to be an effective mechanism to provide additional,
flexible computing capacity to ATLAS. For the first time a total cost of
ownership analysis has been performed, to identify the dominant cost drivers
and explore effective mechanisms for cost control. Network usage significantly
impacts the costs of certain ATLAS workflows, underscoring the importance of
implementing such mechanisms. Resource bursting has been successfully
demonstrated, whilst exposing the true cost of this type of activity. A
follow-up to the project is underway to investigate methods for improving the
integration of cloud resources in data-intensive distributed computing
environments and reducing costs related to network connectivity, which
represents the primary expense when extensively utilising cloud resources.
