Shingled Magnetic Recording (SMR) is a novel disk technology that partially overlaps adjacent disk tracks for high storage density. The partial overlap creates write interference between tracks, and overwriting a track requires to rewrite all its downstream tracks. Inspired by the highly unequal track modify probabilities under real workloads, we propose moving frequently modified tracks toward a downstream, deliberately reserved track, called a guard track, to reduce the extent of write interference. We also introduce a low-cost, seek-optimized scheme for efficient logical-to-physical address mapping. Experimental results showed that our approach outperformed a popular design by 54% and 55% on average in terms of write response time and total disk writes, respectively.