Cooperative caching is one of the key technologies used to improve the performance of a cluster file system. s2fs (scalable single-image file system), a single-image cluster file system prototype, uses dual-granularity cache coherence protocol in order to implement efficient cooperative caching which meets the needs for strict UNIX-semantics. In this paper, a hint-based heuristic cache replacement algorithm under s2fs' dual-granularity protocol is proposed, and the analytical models are established for heuristic algorithm and one of the existing coordinated algorithm——N-chance. The analytical results show that the heuristic algorithm can effectively reduce the I/O response time compared with N-chance algorithm almost in each case.