To explore the opportunity of expanding the page cache using disaggregated memory for file-backed pages, this study presents BalloonStasher, an RDMA-based disaggregated memory for data-intensive applications. Utilizing the ephemeral nature of the page cache, BalloonStasher dynamically adapts to the changing page cache demands of multiple clients. BalloonStasher supports one-sided RDMA-based memory pooling or two-sided RDMA-based memory sharing when using memory nodes. Additionally, it also supports peer memory mode, which utilizes the idle memory of peer nodes. Our extensive performance study compares the benefits and limitations of the three cache modes, and shows that BalloonStasher can mitigate the memory underutilization problem and improve the performance of data-intensive applications by a large margin.