We are proposing a new computational model, called shadow computing, which provides goal-based adaptive resilience using dynamic execution to meet the requirements of complex applications in highly parallelized faulty environments. Adaptive Resilience is the ability of the system to dynamically harness all available resources to achieve the highest level of QoS for a given application. Dynamic execution is the ability to execute an application while being able to change the QoS of that application. For example, we have built systems with the ability to execute processes at variable execution speeds using dynamic voltage and frequency scaling (DVFS), changing the QoS of application response time. The challenge is to maintain applications QoS while minimizing the system resources in spite of systems-level changes, such as failures or the availability of additional system resources. In order to achieve adaptive resilience, the shadow computing model associates a set of shadows to the main execution, which are dynamically instantiated and adjusted in order to address the current state of the system and maintain the application's QoS requirements.
