Fundamental OS Design Considerations for CXL-based Hybrid SSDs

The first commercial implementations of CXL-based hybrid SSDs (i.e., SSDs that are both byte- and block-addressable) are looming on the horizon. Although previous works have conducted design studies on hardware concepts as well as potential use cases, none have analyzed operating system considerations and abstractions for such storage devices. We find existing abstractions (i.e., DAX in Windows and Linux) to be insufficient for hybrid SSDs and propose more appropriate resource management techniques and interfaces in this work. In our evaluation we demonstrate improved throughput by up to 4.1× for applications with strong persistence requirements using the in-memory key-value store Valkey.