When SSDs are used for in-situ execution of data-intensive scientific workflows, it is challenging to obtain consistently high I/O throughput because its I/O efficiency can be compromised for serving write and read requests simultaneously. This issue is so-called write-read interference. In this paper, we propose a novel scheme named FlashStager, which can isolate writes from reads using write redirection to improve data staging performance of SSDs by minimizing the write-read interference. Not only can it detect the interference, but also evaluate whether it is cost-effective to resolve it by executing the write redirection according to its correlation with write ratio and request size. Our experiments with both micro-benchmarks and real scientific applications show than FlashStager can improve I/O performance of staging by 40% on average.