# IOTune: A G-states Driver for Elastic Performance of Block Storage

## TL;DR

IOTune introduces G-states, a middleware for elastic block storage that dynamically adjusts performance levels, improving QoS, reducing latency, and optimizing resource utilization in cloud environments.

## Contribution

The paper presents G-states, a novel resource management middleware using software-defined primitives for elastic performance in block storage, along with a new pricing policy.

## Key findings

- G-states adapt to workload fluctuations effectively.
- G-states reduce I/O tail latencies by 10-100x.
- G-states improve storage utilization and QoS.

## Abstract

Imagining a disk which provides baseline performance at a relatively low price during low-load periods, but when workloads demand more resources, the disk performance is automatically promoted in situ and in real time. In a hardware era, this is hardly achievable. However, this imagined disk is becoming reality due to the technical advances of software-defined storage, which enable volume performance to be adjusted on the fly. We propose IOTune, a resource management middleware which employs software-defined storage primitives to implement G-states of virtual block devices. G-states enable virtual block devices to serve at multiple performance gears, getting rid of conflicts between immutable resource reservation and dynamic resource demands, and always achieving resource right-provisioning for workloads. Accompanying G-states, we also propose a new block storage pricing policy for cloud providers. Our case study for applying G-states to cloud block storage verifies the effectiveness of the IOTune framework. Trace-replay based evaluations demonstrate that storage volumes with G-states adapt to workload fluctuations. For tenants, G-states enable volumes to provide much better QoS with a same cost of ownership, comparing with static IOPS provisioning and the I/O credit mechanism. G-states also reduce I/O tail latencies by one to two orders of magnitude. From the standpoint of cloud providers, G-states promote storage utilization, creating values and benefiting competitiveness. G-states supported by IOTune provide a new paradigm for storage resource management and pricing in multi-tenant clouds.