Compute and memory are tightly coupled within each server in traditional datacenters. Large-scale datacenter operators have identified this coupling as a root cause behind fleet-wide resource underutilization and increasing Total Cost of Ownership (TCO). With the advent of ultra-fast networks and cache-coherent interfaces, memory disaggregation has emerged as a potential solution, whereby applications can leverage available memory even outside server boundaries. This paper summarizes the growing research landscape of memory disaggregation from a software perspective and introduces the challenges toward making it practical under current and future hardware trends. We also reflect on our seven-year journey in the SymbioticLab to build a comprehensive disaggregated memory system over ultra-fast networks. We conclude with some open challenges toward building next-generation memory disaggregation systems leveraging emerging cache-coherent interconnects.

翻译：传统数据中心中，计算与内存紧密耦合于每台服务器内部。大规模数据中心运营商已发现这种耦合是导致全局资源利用率低下及总拥有成本持续攀升的根源。随着超高速网络与缓存一致性接口的出现，内存解耦成为潜在解决方案——应用程序可突破服务器边界利用可用内存。本文从软件视角系统梳理了内存解耦领域不断扩展的研究图景，并剖析了在当前及未来硬件趋势下实现其实用化所面临的挑战。我们同时反思了在SymbioticLab历时七年构建基于超高速网络的全方位解耦内存系统的历程，最后总结了利用新兴缓存一致性互联机制构建下一代内存解耦系统所面临的若干开放挑战。