Jan Harkes

Pervasive Personal Computing in an Internet Suspend/Resume System

The Internet suspend/resume model of mobile computing cuts the tight binding between PC state and PC hardware. By layering a virtual machine on distributed storage, ISR lets the VM encapsulate execution and user customization state; distributed storage then transports that state across space and time. This article explores the implications of ISR for an infrastructure-based approach to mobile computing. It reports on experiences with three versions of ISR and describes work in progress toward the OpenISR version

How close is close enough? Understanding the role of cloudlets in supporting display appropriation by mobile users

Transient use of displays by mobile users was prophesied two decades ago. Today, convergence of a range of technologies enable the realization of this vision. For researchers in this space, one key question is where to physically locate the application for which the display has been appropriated. The emergence of cloud and cloudlet computing has increased the range of possible locations. In this paper we focus on understanding the extent to which application location impacts user experience when appropriating displays. We describe a usage model in which public displays can be appropriated to support spontaneous use of interactive applications, present an example architecture based on cloudlets, and explore how application location impacts user experience.

OpenSlide: A vendor-neutral software foundation for digital pathology

Although widely touted as a replacement for glass slides and microscopes in pathology, digital slides present major challenges in data storage, transmission, processing and interoperability. Since no universal data format is in widespread use for these images today, each vendor defines its own proprietary data formats, analysis tools, viewers and software libraries. This creates issues not only for pathologists, but also for interoperability. In this paper, we present the design and implementation of OpenSlide, a vendor-neutral C library for reading and manipulating digital slides of diverse vendor formats. The library is extensible and easily interfaced to various programming languages. An application written to the OpenSlide interface can transparently handle multiple vendor formats. OpenSlide is in use today by many academic and industrial organizations world-wide, including many research sites in the United States that are funded by the National Institutes of Health.

Transient customization of mobile computing infrastructure

Kimberley is a system that simplifies transient use of fixed hardware infrastructure by a mobile device. It uses virtual machine (VM) technology to resolve the tension between standardizing infrastructure for ease of deployment and maintenance, and customizing that infrastructure to meet the specific needs of a user. Kimberley decomposes the state of a customized VM into a widely-available base VM and a much smaller private VM overlay. The base is downloaded by the infrastructure in advance. Only the small overlay needs to be delivered from the mobile device, or under its control from a public web site. This strategy keeps startup delay low. It may also conserve energy on the mobile device by reducing the volume of wireless transmission. We have built a prototype of Kimberley, and our experiments confirm the feasibility of this approach.

The Case for Content Search of VM Clouds

The success of cloud computing can lead to large, centralized collections of virtual machine~(VM) images. The ability to interactively search these VM images at a high semantic level emerges as an important capability. This paper examines the opportunities and challenges in creating such a search capability, and presents early evidence of its feasibility.

The Case for Offload Shaping

When offloading computation from a mobile device, we show that it can pay to perform additional on-device work in order to reduce the offloading workload. We call this offload shaping, and demonstrate its application at many different levels of abstraction using a variety of techniques. We show that offload shaping can produce significant reduction in resource demand, with little loss of application-level fidelity.

QuiltView: a crowd-sourced video response system

Effortless one-touch capture of video is a unique capability of wearable devices such as Google Glass. We use this capability to create a new type of crowd-sourced system in which users receive queries relevant to their current location and opt-in preferences. In response, they can send back live video snippets of their surroundings. A system of result caching, geolocation and query similarity detection shields users from being overwhelmed by a flood of queries.

Agentless Cloud-Wide Streaming of Guest File System Updates

We propose a non-intrusive approach for monitoring virtual machines (VMs) in the cloud. At the core of this approach is a mechanism for selective real-time monitoring of guest file updates within VM instances. This mechanism is agentless, requiring no guest VM support. It has low virtual I/O overhead, low latency for emitting file updates, and a scalable design. Its central design principle is distributed streaming of file updates inferred from introspected disk sector writes. The mechanism, called DS-VMI, enables many system administration tasks that involve monitoring files to be performed outside VMs.

The unique strengths and storage access characteristics of discard-based search

Discard-based searchis a new approach to searching the content of complex, unlabeled, nonindexed data such as digital photographs, medical images, and real-time surveillance data. The essence of this approach is query-specific content-based computation, pipelined with human cognition. In this approach, query-specific parallel computation shrinks a search task down to human scale, thus allowing the expertise, judgment, and intuition of an expert to be brought to bear on the specificity and selectivity of the search. In this paper, we report on the lessons learned in the Diamond projectfrom applying discard-based search to a variety of applications in the health sciences. From the viewpoint of a user, discard-based search offers unique strengths. From the viewpoint of server hardware and software, it offers unique opportunities for optimization that contradict long-established tenets of storage design. Together, these distinctive end-to-end attributes herald a new genre of Internet applications.

Optimizing Storage Performance for VM-Based Mobile Computing

This article investigates the transient use of free local storage for improving performance in VM-based mobile computing systems implemented as thick clients on host PCs. We use the term TransientPC systems to refer to these types of systems. The solution we propose, called TransPart, uses the higher-performing local storage of host hardware to speed up performance-critical operations. Our solution constructs a virtual storage device on demand (which we call transient storage) by borrowing free disk blocks from the host’s storage. In this article, we present the design, implementation, and evaluation of a TransPart prototype, which requires no modifications to the software or hardware of a host computer. Experimental results confirm that TransPart offers low overhead and startup cost, while improving user experience.