Signature Cache: A Light Weight Web Cache Indexing Structure

Abstract

Current trend in Web cache research is to have Web caches sharing their contents to improve the hit ratio. High performance Web cache sharing requires use of access indexes for Web caches to reference each other. The challenges facing the design of access indexes for Web cache sharing are the huge size, dynamic nature of Web cache contents, and high access speed. A recently proposed summary cache scheme [14] uses relatively small indexes for sharing Web caches to reference each other. We improved the summary cache scheme and propose a signature cache scheme. Instead of "repairing" existing access indexes, signature cache scheme builds new indexes to accommodate changes of Web cache contents. This scheme simplifies the maintenance of the indexes and significantly reduces the size of counters. Optionally, the size of the index can be further reduced by a semi-distributed index sharing mode at the cost of slightly increased response time. These improvements result in orders of magnitude reduction in the index size as compared to the summary cache scheme.