Maximizing Interconnect Bandwidth and Efficiency in NVMe-Based Key-Value SSDs with Fine-Grained Value Transfer

The Key-Value SSD (KV-SSD) redefines storage interfaces by integrating a key-value store directly within the device, offering native support for non-page-aligned key-value pairs. This architectural innovation enables KV-SSDs to offload storage management from the host system, positioning them as ideal candidates for resource disaggregation. However, KV-SSDs face significant challenges, notably I/O amplification caused by conflicts with traditional storage protocols like NVMe, which are designed around memory page units. Specifically, this results in a substantial increase in data traffic over interconnect between the host and SSD. This paper introduces BandSlim, a novel solution addressing these challenges in data transfer by leveraging (i) NVMe command piggybacking for universally compatible, fine-grained transfers without requiring interconnect-level support and (ii) the remote memory access capabilities of emerging Compute eXpress Link (CXL) interconnects for higher-performance fine-grained transfers. Through extensive evaluations, BandSlim achieves up to a 97.9% reduction in PCIe traffic compared to conventional NVMe KV-SSDs.