P-Cache to provide prioritized caching service for storage server which is used to serve multiple concurrently accessing applications with diverse access patterns and unequal importance. Given the replacement algorithm and the application access patterns, the end performance of each individual application in a shared cache is actually determined by its allocated cache resource. So, P-Cache adopts a dynamic partitioning approach to explicitly divide cache resource among applications and utilizes a global cache allocation policy to make adaptive cache allocations to guarantee the preset relative caching priority among competing applications. We have implemented P-Cache in Linux kernel 2.6.18 as a pseudo device driver and measured its performance using synthetic benchmark and real-life workloads. The experiment results show that the prioritized caching service provided by P-Cache can not only be used to support application priority but can also be utilized to improve the overall storage system performance. Its runtime overhead is also smaller compared with Linux page cache.