Cloud vs Grid

The effective use of a Cloud is dependent on the applications. The Cloud can be used appropriately when dealing with linear processes and independent, relatively small data volumes. For applications with larger storage requirements or closely coupled parallel processes with high I/O requirements, Clouds are often useless [here].

Grid works at the "library level" where the users are provided an known "environment" in which their applications should be able to run. In a sense cloud computing offers what grid cannot, a predictable execution environment [here].

Some links from second source:
- Benchmarking Amazon EC2 for High-performance Scientific Computing
- Can Cloud Computing Reach The TOP500?
- HPC in the Cloud