The common bottleneck of web proxy servers is disk I/O. Most general-purpose file systems are very inefficient on handling web cache workload and have high overloads. In this paper we are interested in exploring a way to reduce disk I/O overhead by using raw disk instead of the file system. To show the superior performance potential of raw disk approach, we design a simple Block-structured Storage Management System (BSMS) and implement Web Proxy Server over RAW disk (WPS-RAW) that incorporates BSMS in Squid. Comprehensive experimental evaluations by using the Web Polygraph proxy performance benchmark suggest that raw disk can be a good solution to improve disk I/O performance of web proxy server significantly.