By carefully studying the characteristics of IPTV (Internet Protocol TeleVision) live streaming service supporting timeshift functions, we find the default disk I/O strategies of universal OS can not provide satisfactory performance. Based on these observations, this paper proposes a set of dedicated disk I/O strategies in the design and implementation of a live streaming server supporting timeshift functions. Our proposed strategies include asynchronous direct I/O, block-level data processing, media caching and media prefetching, which are implemented in a live streaming server (ClearServer) developed by ourselves. ClearServer has been successfully deployed in the Shanghai Zhabei IPTV test-bed. Based on the deployment, detailed performance evaluation and test results demonstrate that the proposed strategies significantly improve several major performance metrics of the IPTV live streaming servers.