A QoS aware non-work-conserving disk scheduler

Disk schedulers should provide QoS guarantees to applications, thus sharing proportionally the storage resource and enforcing performance isolation. Disk schedulers must execute requests in an efficient order though, preventing poor disk usage. Non-work-conserving disk schedulers help to increase disk throughput by predicting future requests' arrival and therefore exploiting disk spatial locality. Previous work are limited to either provide QoS guarantees or exploit disk spatial locality. In this paper, we propose a new non-work-conserving disk scheduler called High-throughput Token Bucket Scheduler (HTBS), which can provide both QoS guarantees and high throughput by (a) assigning tags to requests in a fair queuing-like fashion and (b) predicting future requests' arrival. We show through experiments with our Linux Kernel implementation that HTBS outperforms previous QoS aware work-conserving disk schedulers throughput as well as provides tight QoS guarantees, unlike other non-work-conserving algorithms.