With the developments of network technologies, many mechanisms have been introduced to improve system performance in cluster systems by exploiting remote idle memory. However, none of them can satisfy the requirements from different applications. Most methods can only improve the performance of a particular type of applications but not for others. One important reason is they failed to provide unified interfaces. In this paper, we propose Collaborative Memory Pool (CMP) to solve this problems. CMP brings scalability and high performance. It has five features: 1) Providing malloc-like interfaces, block device interfaces and kernel API for different applications, which benefit both user-level and kernel-level applications; 2) Retaining traditional VM mechanism, programmers and uses have the freedom to select CMP or not; 3) Improving kernel applications performance by eliminating remote swapping; 4) Avoiding loan while in debt problem with dynamic workload; 5) Providing optional memory servers to further improve performance. In our testbed with CMP-based swap devices, Qsort gets 83.28% improvement comparing with the case using disk-based swap devices.