Abstract: I/O is a major performance bottleneck in modern computer systems. Modern disks use the Zone-Bit-Recording (ZBR) technology to increase the capacity. A direct consequence of ZBR is that outer tracks have higher data transfer rates. Because LFS uses large disk transfers, access times are mainly determined by the data transfer rate. This paper presents a novel performance-oriented data reorganizing scheme, called PROFS, which boosts the I/O performance of LFS (Log-structured File System). Our scheme reorganizes data on the disk during LFS garbage collection and system idle periods. By putting active data in the faster zones and inactive data in the slower zones, we can significantly improve the read and write performance. The reorganization overhead is minimal. We studied three different algorithms that are read-optimized, write-optimized and balanced. Simulation results based on five real-world and two synthetic traces showed that such algorithms can dramatically reduce the I/O response time for both reads and writes compared with the most recent LFS systems with adaptive methods. Our algorithms improve the LFS system's write latency by up to 24.5% and the read latency by up to 21.3%.They also improve the file system throughput by up to 32%.