CER-IOS: Internal Resource Utilization Optimized I/O Scheduling for Solid State Drives

Modern Solid State Drives (SSDs) integrate more internal resources to get higher performance and capacity. Improving internal resource utilization by exploiting internal parallelism is important to enhance the performance of SSDs. Unfortunately, the internal resource utilization of SSDs is limited at runtime in practice because of the practical access conflicts to internal resources. In this paper, we propose a Conflict Eliminated Requests Based I/O Scheduler (CER-IOS) to better utilize internal parallelism of flash chips by scheduling I/O requests in a more fine-grained way. We introduce Conflict Eliminated Requests (CERs) in which parallelizable memory requests are grouped during the process of address translation in Flash Translation Layer. To schedule conflicting requests, we propose a small CER size prioritized resource distribution scheme, that ensures internal resources can always be distributed to valuable conflicting requests to further improve the efficiency of resource utilization. Our extensive experimental evaluation results show that CER-IOS provides significant improvement of resource utilization at runtime and reduces average I/O latency largely compared to state-of-the-art I/O schedulers implemented in operating systems.