Efficient cooperative caching for file systems in cluster-based Web servers

Most of the traditional cooperative caching schemes were developed so that remote users may share files in network file systems, but were not designed for supporting recent cluster based Web servers with content based request distribution. For this reason, although the schemes are applied to the Web servers, their performance suffers from high disk accesses and large block access latency. The paper proposes and evaluates a new cooperative caching suitable for file systems in the Web servers. By exploiting the characteristics of the Web servers, it performs a cache replacement, called Duplicate First copy Replacement (DFR) to avoid caching unnecessary data produced during serving remote client requests, and thus minimizes disk accesses. Also, it reduces the overhead and block access latency required to fetch a file block (or page) in the cooperative cache with regard to both the content based Web server architecture and characteristics. Trace-driven simulation shows that our cooperating caching decreases the disk access ratio by 29%, and reduces block access latency by about 26% more than the existing cooperative algorithms.