The growing prevalence of data-intensive workloads, such as artificial intelligence (AI), machine learning (ML), high-performance computing (HPC), in-memory databases, and real-time analytics, has exposed limitations in conventional memory technologies like DRAM. While DRAM offers low latency and high throughput, it is constrained by high costs, scalability challenges, and volatility, making it less viable for capacity-bound and persistent applications in modern datacenters. Recently, Compute Express Link (CXL) has emerged as a promising alternative, enabling high-speed, cacheline-granular communication between CPUs and external devices. By leveraging CXL technology, NAND flash can now be used as memory expansion, offering three-fold benefits: byte-addressability, scalable capacity, and persistence at a low cost. Samsung's CXL Memory Module Hybrid (CMM-H) is the first product to deliver these benefits through a hardware-only solution, i.e., it does not incur any OS and IO overheads like conventional block devices. In particular, CMM-H integrates a DRAM cache with NAND flash in a single device to deliver near-DRAM latency. This paper presents the first publicly available study for comprehensive characterizations of an FPGA-based CMM-H prototype. Through this study, we address users' concerns about whether a wide variety of applications can successfully run on a memory device backed by NAND flash medium. Additionally, based on these characterizations, we provide key insights into how to best take advantage of the CMM-H device.

翻译：随着人工智能（AI）、机器学习（ML）、高性能计算（HPC）、内存数据库和实时分析等数据密集型工作负载日益普及，传统内存技术（如DRAM）的局限性逐渐暴露。尽管DRAM具有低延迟和高吞吐量的优势，但其高昂成本、可扩展性挑战以及易失性等特点，使其在现代数据中心中难以满足容量受限型应用和持久性应用的需求。近年来，计算快速链接（CXL）作为一种有前景的替代方案崭露头角，它支持CPU与外部设备之间进行高速、缓存行粒度的通信。通过利用CXL技术，NAND闪存现可作为内存扩展使用，提供三大优势：字节可寻址性、可扩展容量以及低成本持久性。三星CXL内存模块混合（CMM-H）是首款通过纯硬件解决方案实现这些优势的产品，即它不会像传统块设备那样产生任何操作系统和I/O开销。特别地，CMM-H在单一设备中集成了DRAM缓存与NAND闪存，以提供接近DRAM的延迟。本文首次公开了对基于FPGA的CMM-H原型进行全面特征分析的研究。通过此项研究，我们回应了用户对各类应用能否在基于NAND闪存介质的内存设备上成功运行的关切。此外，基于这些特征分析，我们为如何最佳利用CMM-H设备提供了关键见解。