I/O scheduling for solid state devices in virtual machines

Solid State Devices (SSD) are supplementing and gradually replacing traditional mechanical hard drives to become the mainstream of storage devices with better performance and lower power consumption. However, the disk I/O schedulers designed for traditional disks do not consider the characteristics of SSDs. Additionally in a virtualized environment the virtual machines I/O requests would be scheduled twice, in guest and host OSes. The request latency characteristics observed at both places are quite different. Based on the characteristics of SSD, we design an adaptive I/O scheduler which gives read requests higher priority and further analyze the best possible combination of I/O schedulers for the guest and host OSes. The experimental results show that the average delay of read requests with our adaptive scheduler is reduced by about 11.55 percent compared to the I/O scheduler with fixed dispatch ratio of read and writes requests. Meanwhile, when the guest and the host both adopt our scheduler, its average delay outperforms others by about 11.13 percent.