Efficient QoS for Multi-Tiered Storage Systems
Multi-tiered storage systems using tiers of SSD and traditional hard disk is one of the fastest growing trends in the storage industry. Although using multiple tiers provides a flexible trade-off in terms of IOPS performance and storage capacity, the authors believe that providing performance isolation and QoS guarantees among various clients, gets significantly more challenging in such environments. Existing solutions focus mainly on either disk-based or SSD-based storage back-ends. In particular, the notion of IO cost that is used by existing solutions gets very hard to estimate or use. In this paper, they first argue that providing QoS in multi-tiered systems is quite challenging and existing solutions aren't good enough for such cases.