The Internet is undergoing substantial changes from a communication and browsing infrastructure to a medium for conducting business and marketing a myriad of services. The World Wide Web provides a uniform and widely-accepted application interface used by these services to reach multitudes of clients. These changes place the web server at the center of a gradually emerging eservice infrastructure with increasing requirements for service quality and reliability guarantees in an unpredictable and highly-dynamic environment.

One of the most important goals of data-center management is to reduce cost through efficient use of resources. Virtualization techniques provide the opportunity of carving individual physical servers into multiple virtual containers that can be run and managed separately. A key challenge that comes with virtualization is the simultaneous on-demand provisioning of shared resources to virtual containers and the management of their capacities to meet service quality targets at the least cost. This paper proposes a two-level resource management system with local controllers at the virtual-container level and a global controller at the resource-pool level. Autonomic resource allocation is realized through the interaction of the local and global controllers. A novelty of the controller designs is their use of fuzzy logic to efficiently and robustly deal with the complexity of the virtualized data center and the uncertainties of the dynamically changing workloads. Experimental results obtained through a prototype implementation demonstrate that, for the scenarios under consideration, the proposed resource management system can significantly reduce resource consumption while still achieving application performance targets. 1.

Virtual Machines are becoming increasingly valuable to resource consolidation and management, providing efficient and secure resource containers, along with desired application execution environments. This paper focuses on the VM-based resource reservation problem, that is, the reservations of CPU, memory and network resources for individual VM instances, as well as for VM clusters. In particular, it considers the scenario where one or several physical servers need to be vacated to start a cluster of VMs for dedicated execution of parallel jobs. VMs provide a primitive for transparently vacating workloads through migration; however, the process of migrating several VMs can be timeconsuming and needs to be estimated. To achieve this goal, this paper seeks to provide a model that can characterize the VM migration process and predict its performance, based on a comprehensive experimental analysis. The results show that, given a certain VM’s migration time, it is feasible to predict the time for a VM with other configurations, as well as the time for migrating a number of VMs. The paper also shows that migration of VMs in parallel results in shorter aggregate migration times, but with higher per-VM migration latencies. Experimental results also quantify the benefits of buffering the state of migrated VMs in main memory without committing to hard disks. 1.

As Internet expands, the number of application servers, especially Web servers, has been increasing exponentially.

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Recent highly publicized benchmarks have suggested that Linux systems do not scale as well as other systems, such as Windows NT, when used as network servers. Windows NT contains features such as I/O completion ports that help boost network server performance and scalability. In this paper we focus on improving the Linux implementation of poll() to reduce the expense of managing large numbers of network connections. We also explore the newer POSIX RT signal API that will help network servers scale into the next decade. A comparison between the two interfaces shows that a server using our /dev/poll interface scales better than a server using RT signals. May 2, 2000 Center for Information Technology Integration University of Michigan 519 West William Street Ann Arbor, MI 48103-4943 This document was written as part of the Linux Scalability Project. The work described in this paper was supported via grants from the Sun-Netscape Alliance, Intel, Dell, and IBM. For more information, see our home page. If you have comments or suggestions, email <linux-scalability@citi.umich.edu> Copyright 2000 by the Regents of the University of Michigan, and by AOL-Netscape Inc. All rights reserved. Trademarked material referenced in this document is copyright by its respective owner. Scalable Network I/O in Linux Niels Provos, University of Michigan Chuck Lever, Sun-Netscape Alliance 1.