Gimbal: enabling multi-tenant storage disaggregation on SmartNIC JBOFs

Emerging SmartNIC-based disaggregated NVMe storage has become a promising storage infrastructure due to its competitive IO performance and low cost. These SmartNIC JBOFs are shared among multiple co-resident applications, and there is a need for the platform to ensure fairness, QoS, and high utilization. Unfortunately, given the limited computing capability of the SmartNICs and the non-deterministic nature of NVMe drives, it is challenging to provide such support on today's SmartNIC JBOFs. This paper presents Gimbal, a software storage switch that orchestrates IO traffic between Ethernet ports and NVMe drives for co-located tenants. It enables efficient multi-tenancy on SmartNIC JBOFs using the following techniques: a delay-based SSD congestion control algorithm, dynamic estimation of SSD write costs, a fair scheduler that operates at the granularity of a virtual slot, and an end-to-end credit-based flow control channel. Our prototyped system not only achieves up to x6.6 better utilization and 62.6% less tail latency but also improves the fairness for complex workloads. It also improves a commercial key-value store performance in a multi-tenant environment with x1.7 better throughput and 35.0% less tail latency on average.