This paper presents the design, implementation, and evaluation of IO-Lite, a unified I/O buffering and caching system. IO-Lite unifies all buffering and caching in the system, to the extent permitted by the hardware. In particular, it allows applications, interprocess communication, the filesystem, the file cache, and the network subsystem to share a single physical copy of the data safely and concurrently. Protection and security are maintained through a combination of access control and read-only sharing. The various subsystems use (mutable) buffer aggregates to access the data according to their needs. IO-Lite eliminates all copying and multiple buffering of I/O data, and enables various cross-subsystem optimizations. Performance measurements show significant performance improvements on Web servers and other I/O intensive applications. 1 Introduction This paper presents the design, the implementation, and the performance of IO-Lite, a unified I/O buffering and caching system. IO-Li...

Under high loads, a Web server may be servicing manyhundreds of connections concurrently. In traditional

This paper studies mechanisms and policies for supporting HTTP/1.1 persistent connections in cluster-based Web servers that employ content-based request distribution. We present two mechanisms for the efficient, content-based distribution of HTTP/1.1 requests among the back-end nodes of a cluster server. A trace-driven simulation shows that these mechanisms, combined with an extension of the locality-aware request distribution (LARD) policy, are effective in yielding scalable performance for HTTP/1.1 requests. We implemented the simpler of these two mechanisms, back-end forwarding. Measurements of this mechanism in connection with extended LARD on a prototype cluster, driven with traces from actual Web servers, con rm the simulation results. The throughput of the prototype is up to four times better than that achieved by conventional weighted round-robin request distribution. In addition, throughput with persistent connections is up to 26 % better than without.