Optically Connected Memory for Disaggregated Data Centers

• Jorge Gonzalez UNICAMP
• Alexander Gazman Columbia University
• Maarten Hattink Columbia University
• Mauricio G. Palma UNICAMP
• Meisam Bahadori Nokia
• Ruth Rubio-Noriega INICTEL-UNI
• Lois Orosa ETH Zürich
• Madeleine Glick Columbia University
• Onur Mutlu ETH Zürich
• Keren Bergman Columbia University
• Rodolfo Azevedo UNICAMP

Abstract

Recent advances in integrated photonics enable the implementation of reconfigurable, high-bandwidth, and low energy-per-bit interconnects in next-generation data centers. We propose and evaluate an Optically Connected Memory (OCM) architecture that disaggregates the main memory from the computation nodes in data centers. OCM is based on micro-ring resonators (MRRs), and it does not require any modification to the DRAM memory modules. We calculate energy consumption from real photonic devices and integrate them into a system simulator to evaluate performance. Our results show that (1) OCM is capable of interconnecting four DDR4 memory channels to a computing node using two fibers with 1.07 pJ energy-per-bit consumption and (2) OCM performs up to 5.5x faster than a disaggregated memory with 40G PCIe NIC connectors to computing nodes.

Keywords: Memory management, Optical receivers, Optical resonators, Optical pulses, Optical fiber communication, Bandwidth, Random access memory, disaggregated computing, disaggregated memory, photonics, data-centers, DRAM, memory systems