Marty Humphrey

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One of many advantages of the cloud is the elasticity, the ability to dynamically acquire or release computing resources in response to demand. However, this elasticity is only meaningful to the cloud users when the acquired Virtual Machines (VMs) can be provisioned in time and be ready to use within the user expectation. The long unexpected VM startup time(More)
The MyProxy online credential repository has been used by the grid computing community for over four years for managing security credentials in the grid public key infrastructure. MyProxy improves usability by giving users access to their credentials over the network using password authentication, allowing users to delegate their credentials via web browser(More)
Building distributed embedded systems from scratch is not cost-effective. Instead, designing and building these systems by using domain specific components has promise. However, in using components, the most difficult issues are ensuring that hidden dependencies won't cause failures and that non-functional properties such as real-time performance are being(More)
A goal in cloud computing is to allocate (and thus pay for) only those cloud resources that are truly needed. To date, cloud practitioners have pursued schedule-based (e.g., time-of-day) and rule-based mechanisms to attempt to automate this matching between computing requirements and computing resources. However, most of these "auto-scaling" mechanisms only(More)
Clouds have become an attractive computing platform which offers on-demand computing power and storage capacity. Its dynamic scalability enables users to quickly scale up and scale down underlying infrastructure in response to business volume, performance desire and other dynamic behaviors. However, challenges arise when considering computing instance(More)
This paper describes a formal feedback-control algorithm for dynamic voltage/frequency scaling (DVS) in a portable multimedia system to save power while maintaining a desired playback rate. Our algorithm is similar in complexity to the previously-proposed change-point detection algorithm [19] but does a better job of maintaining stable throughput and is not(More)
A significant open issue in cloud computing is performance. Few, if any, cloud providers or technologies offer quantitative performance guarantees. Regardless of the potential advantages of the cloud in comparison to enterprise-deployed applications, cloud infrastructures may ultimately fail if deployed applications cannot predictably meet behavioral(More)
Securing a Grid environment presents a distinctive set of challenges. This work groups the activities that need to be secured into four categories: naming and authentication; secure communication; trust, policy, and authorization; and enforcement of access control. It examines the current state of the art in securing these activities and introduces new(More)
The introduction of affordable infrastructure on demand, specifically Amazon's Elastic Compute Cloud (EC2), has had a significant impact in the business IT community and provides reasonable and attractive alternatives to locally-owned infrastructure. For scientific computation however, the viability of EC2 has come into question due to its use of(More)
The problem with the grid is that it does not currently extend completely to devices, because these devices are not viewed as having sufficient capability to be both clients and services. We design, implement and evaluate Mobile OGSI.NET, which extends an implementation of grid computing, OGSI.NET, to mobile devices. Mobile OGSI.NET addresses the mobile(More)