YouChoose: A performance interface enabling convenient and efficient QoS support for consolidated storage systems

Currently the QoS requirements for disk-based storage systems are usually presented in the form of service-level agreement (SLA) to bound I/O measures such as latency and throughput of I/O requests. However, SLA is not an effective performance interface for users to specify their required I/O service quality for two major reasons. First, for users, it is difficult to determine appropriate latency and throughput bounds to ensure their application performance without resource over-provisioning. Second, for storage system administrators, it is a challenge to estimate a user´s real resource demand because the specified SLA measures are not consistently correlated with the user´s resource demand. This makes resource provisioning and scheduling less informative and could greatly reduce system efficiency. We propose the concept of reference storage system (RSS), which can be a storage system chosen by users and whose performance can be measured off-line and mimicked on-line, as a performance interface between applications and storage servers. By designating an RSS to represent I/O performance requirement, a user can expect the performance received from a shared storage server servicing his I/O workload is not worse than the performance received from the RSS servicing the same workload. The storage system is responsible for implementing the RSS interface. The key enabling techniques are a machine learning model that derives request-specific performance requirements and an RSS-centric scheduling that efficiently allocates resource among requests from different users. The proposed scheme, named as YouChoose, supports the user-chosen performance interface through efficiently implementing and migrating virtual storage devices in a host storage system. Our evaluation based on trace-driven simulations shows that YouChoose can precisely implement the RSS performance interface, achieve a strong performance assurance and isolation, and improve the efficiency of a consolidated stor- - age system consisting of different types of storage devices.