Understanding and Monitoring Cloud Services

Cloud services have changed the way computing power is delivered to customers. The advantages of the cloud model have fast resulted in powerful providers. However, this success has not come without problems. Cloud providers have been related to major failures, including outages and performance degradation. Similarly, privacy of cloud services is of huge concern for exposing users to providers and foreign governments. We argue that dependability concerns will impel enterprises to require assurances and independent monitoring of their services in the cloud. Privacy issues will prompt new players to offer services that combine the strengths of cloud computing with stronger privacy. Initial signs of both trends can already be mentioned, such as companies offering independent tools to monitor cloud performance and regional players entering the cloud market while worldwide firms hesitate to trust international providers. This thesis has two objectives. Firstly, we investigate simple and scalable methods for monitoring the performance of cloud services, aiming to provide means for customers to monitor their services easily and independently. Secondly, we study how cloud services are implemented and the implications of their design and usage for the Internet, aiming to foster the development of new services. We focus on cloud storage, because it is a popular application accounting for a significant share of Internet traffic. Our main contributions are the following: (i) we introduce a novel method to monitor the performance of cloud services, relying on flow measurements collected from customers' networks; (ii) we present the first characterization of cloud storage, revealing its typical usage and possible performance bottlenecks; and (iii) we evaluate the implications of design choices for both users and the Internet, by comparing different providers in a series of benchmarks. Our analyses show that cloud services can be monitored using information available at customers' networks. Our results make clear that cloud storage is data-intensive and understanding its usage is essential for building well-performing services. Our comparisons of providers demonstrate that design differences that seem minor can result in surprisingly costs and performance bottlenecks. Our contributions are valuable for companies outsourcing to the cloud and for engineers developing cloud storage, and can assist new players to build the next generation of cloud storage services.