Efficient Disk I/O Scheduling with QoS Guarantee for Xen-based Hosting Platforms

In this paper, we address the problem of allocating disk resources to guarantee specified latency and throughput targets of VMs while keeping efficient disk I/O. Accordingly, we present two-level scheduling framework, namely Flubber, in Xen-based hosting platform that decouples latency and throughput allocation. The high-level throughput control regulates the pending requests from the VMs, in order to meet the throughput requirements of different VMs and ensure isolation. Meanwhile, the low-level latency control, by the virtue of the batch and delay EDF mechanism, reorders all pending requests from VMs based on the their deadlines, and batches them to the disk device considering the locality of accesses across VMs. We have implemented Flubber with intensive evaluations on Xen-based host. The results show that Flubber can simultaneously meet the different service requirements of VMs while improving the efficiency of the physical disk. In contrast to CFQ, besides that Flubber achieves the desired QoS of each VM, Flubber speeds up the sequential and random read by 17% and 25% due to the efficient physical disk utilization.