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Colloquium - Voelker

Cooperative Caching in Local-Area and Wide-Area Networks
University of Washington
4/8/1999
3:45pm-4:45pm

Cooperative caching systems manage a set of distributed caches as a single, global resource. Managed globally, these caches can be significantly more effective than the collection of independently operated caches. In this talk, I will describe work on cooperative caching systems for two interesting, although fundamentally different, network domains: workstation clusters and the Internet.

In the workstation cluster environment, the cooperative caching system manages the primary memories of all cluster nodes, providing a cluster-wide cache for virtual memory and file data. When there is idleness in the cluster, processes running on active nodes can use the memories of idle nodes as a new level of backing store, instead of (or in addition to) the local disk. With network speeds greatly outpacing disk speeds, a fault handled over the network from such a "remote memory" can be up to 50 times faster than a local disk fault. Even with this difference, however, some applications remain heavily I/O bound. In the first half of this talk, I will describe the design and implementation of a new system that combines cooperative caching with file prefetching to further reduce the disk I/O bottleneck for these applications.

In the context of the Web, the standard mechanism for improving performance is the proxy cache, which sits between multiple clients and the Internet. A number of wide-area cooperative proxy caching systems have been proposed in an attempt to improve the cache performance. However, the effectiveness of such schemes ultimately depends upon the degree of document sharing among clients, as well as the cost of communication among proxies. In the second half of the talk, I will describe a study of document sharing among clients that we have conducted to understand the potentials of proxy cache organizations. The study is based on traces of Web traffic from all clients in the University of Washington to servers in the Internet that we have been collecting since October 1998. I will present initial results of UW as a case study for cooperative Web caching, and will describe the implications of scaling cooperative Web caching systems to millions of clients.

Hosted by Gary Nutt.
Refreshments will be served prior to the talk at 3:30pm.

Department of Computer Science
University of Colorado Boulder
Boulder, CO 80309-0430 USA
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