A general framework for dynamic and automatic I/O scheduling in hard and solid-state drives

• DADS concurrently compares several I/O schedulers in real time.
• DADS automatically selects the I/O scheduler that provides the best performance.
• DADS works at any time for any workload without previous knowledge.
• DADS can be used in both hard disks and solid state drives.
• System administrators are exempted from selecting a suboptimal I/O scheduler.

The selection of the right I/O scheduler for a given workload can significantly improve the I/O performance. However, this is not an easy task because several factors should be considered, and even the “best” scheduler can change over the time, specially if the workload’s characteristics change too. To address this problem, we present a Dynamic and Automatic Disk Scheduling framework (DADS) that simultaneously compares two different Linux I/O schedulers, and dynamically selects that which achieves the best I/O performance for any workload at any time. The comparison is made by running two instances of a disk simulator inside the Linux kernel. Results show that, by using DADS, the performance achieved is always close to that obtained by the best scheduler. Thus, system administrators are exempted from selecting a suboptimal scheduler which can provide a good performance for some workloads, but may downgrade the system throughput when the workloads change.