We present PD-Survey, a platform to conduct surveys across a network of interactive screens. Our research is motivated by the fact that obtaining and analyzing data about users of public displays requires signi cant effort; e.g., running long-term observations or post-hoc analyses of video/interaction logs. As a result, research is often constrained to a single installation within a particular context, neither accounting for a diverse audience (children, shoppers, commuters) nor for different situations (waiting vs. passing by) or times of the day. As displays become networked, one way to address this challenge is through surveys on displays, where audience feedback is collected insitu. Since current tools do not appropriately address the requirements of a display network, we implemented a tool for use on public displays and report on its design and development. Our research is complemented by two in-the-wild deployments that (a) investigate di erent channels for feedback collection, (b) showcase how the work of researchers is supported, and (c) testify that the platform can easily be extended with novel features.

Virtualization technology allows a dynamic allocation of VMs to servers. It reduces server demand and increases energy efficiency of data centers. Dynamic control strategies migrate VMs between servers in dependence to their actual workload. A concept that promises further improvements in VM allocation efficiency. In this paper we evaluate the applicability of DSAP in a deterministic environment. DSAP is a linear program, calculating VM allocations and live-migrations on workload patterns known a priori. Efficiency is evaluated by simulations as well as an experimental test bed infrastructure. Results are compared against alternative control approaches that we studied in preliminary works. Our findings are, dynamic allocation can reduce server demand at a reasonable service quality. Countermeasures are required to keep the number of live-migrations under control.