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In classical machine virtualization, a hypervisor runs multiple operating systems simultaneously, each on its own virtual machine. In nested virtualization, a hypervi-sor can run multiple other hypervisors with their associated virtual machines. As operating systems gain hyper-visor functionality—Microsoft Windows 7 already runs Windows XP in a virtual(More)
This work investigates personalized social search based on the user's social relations -- search results are re-ranked according to their relations with individuals in the user's social network. We study the effectiveness of several social network types for personalization: (1) Familiarity-based network of people related to the user through explicit(More)
This paper extends traditional faceted search to support richer information discovery tasks over more complex data models. Our first extension adds exible, dynamic business intelligence aggregations to the faceted application, enabling users to gain insight into their data that is far richer than just knowing the quantities of documents belonging to each(More)
Direct device assignment enhances the performance of guest virtual machines by allowing them to communicate with I/O devices without host involvement. But even with device assignment, guests are still unable to approach bare-metal performance, because the host intercepts all interrupts, including those interrupts generated by assigned devices to signal to(More)
We explore new ways of improving a search engine using data from Web 2.0 applications such as blogs and social bookmarks. This data contains entities such as documents, people and tags, and relationships between them. We propose a simple yet effective method, based on faceted search, that treats all entities in a unified manner: returning all of them(More)
— Storage cloud systems achieve economies of scale by serving multiple tenants from a shared pool of servers and disks. This leads to the commingling of data from different tenants on the same devices. Typically, a request is processed by an application running with sufficient privileges to access any tenant's data; this application authenticates the user(More)
The most popular I/O virtualization method today is paravirtual I/O. Its popularity stems from its reasonable performance levels while allowing the host to interpose, i.e., inspect or control, the guest's I/O activity. We show that paravirtual I/O performance still significantly lags behind that of state-of-the-art non-interposing I/O virtualization, SRIOV.(More)
Virtual machines in the cloud typically run existing general-purpose operating systems such as Linux. We notice that the cloud's hypervisor already provides some features, such as isolation and hardware abstraction, which are duplicated by traditional operating systems, and that this duplication comes at a cost. We present the design and implementation of(More)
Virtualization is a prominent technology used in data centers around the world. While many kinds of workloads can run at near-native performance even when virtualized, I/O intensive workloads still suffer from high overhead precluding the use of virtualization in many applications. In this paper we tackle the problem of improving the performance of(More)