TCO-driven Storage Provisioning for Exascale Data Centers

Recent changes in data temperatures and storage device characteristics, both mechanical disk-drives (HDDs) and solidstate drives (SSDs), expand the set of deployment options for exascale storage. Until recently, exascale storage systems followed a pattern of placing most data on HDDs with smaller amounts of SSD storage used for caching and performancecritical workloads. Exascale storage provisioning and dataset placement trade-offs have now changed.

This paper describes a total cost of ownership (TCO) model that captures primary aspects of modern deployments and uses it to explore the new trade-off space. Using capacity and performance telemetry information for 43 production datasets+workloads at two large hyperscalers, we show significant changes from prior analyses of workloads and storage placement decisions across a multitude of storage device types. We also introduce a storage cluster TCO optimizer that identifies the lowest-TCO grouping and assignment of datasets to device types, exposing a number of insights that can help guide future deployments. For example, our analysis shows that the highest-density SSDs are particularly favorable for clusters with heavy AI/ML workloads but are only cost-effective at exascale when combined with high-density HDDs. Finally, we use our framework to evaluate how storage provisioning and overall TCO change as a function of key parameters like device write amplification, cluster power bounds, and the maximum number of device types allowed.