File Fragmentation from the Perspective of I/O Control

File fragmentation has been widely studied for several decades due to its detrimental effects on I/O activities. However, most of the previous research focuses on its performance aspect in a single application. In this paper, we analyze the effect of fragmentation on I/O control in a consolidated system where multiple applications run simultaneously. Our evaluation demonstrates that all of the weight-based I/O control mechanisms supported by the Linux kernel fail to achieve fair I/O sharing for different reasons when they meet fragmentation. Also, we show that defragmentation can promptly antidote such failures by preventing request splitting and device-level resource conflicts.