Increasing Spot Instances Reliability Using Dynamic Scalability

Traditionally, Infrastructure as a Service (IaaS)providers deliver their services as Reserved or On-Demand instances. Spot Instances (SIs) is a complementary service that allows customers to bid on the free capacity at the provider data centers. Therefore, the decrease in the free capacity may result in terminating instances abruptly. To ensure fair trading, the provider does not charge customers for the interrupted partial hours. However, SIs price history traces analysis shows that uncharged time could rise up to 30% of the instance total run time, which means a reduction in the provider´s profit. In this paper, we propose Elastic Spot Instances (ESIs) approach. It is a trade-off between the price and the total run time, where instead of abruptly terminating the SIs, the provider scales down their capacity proportionally to the increase in the price. Our approach delegates the task of interrupting the instances into the customers, but at the same time keeps the control on the provider side to isolate SIs´ impact on the other services at overloaded time. Our approach doesn´t imply an additional overhead or complex modification to current IaaS, while it consumes interfaces that are available by most of nowadays virtualization technologies.