Summit (OLCF-4) is a 200-petaFLOP supercomputer operating by the DoE Oak Ridge National Laboratory. Summit was officially unveiled on June 8, 2018 as the fastest supercomputer in the world, overtaking Sunway TaihuLight.

History

Summit is one of three systems as part of the Collaboration of Oak Ridge, Argonne, and Lawrence Livermore Labs (CORAL) procurement program. Research and planning started in 2012 with initial system delivery arriving in late 2017. The full system arrived in early 2018 and the system was officially unveiled on June 8, 2018. Summit is estimated to have cost around $200 million as part of the CORAL procurement program.

Overview

Summit was designed to deliver 5-10x improvement in performance for real big science workload performance over Titan. Compared to Titan which had 18,688 nodes (AMD Opteron + Nvidia Kepler) with a 9 MW power consumption, Summit slightly increased the power consumption to 13 MW, reduced the number of nodes to only 4,608, but tenfold the peak theoretical performance from 27 petaFLOPS to around 225 PF.

Summit has over 200 petaFLOPS of theoretical compute power and over 3 AI exaFLOPS for AI workloads.

	Components				System
Processor	CPU	GPU		Rack	Compute Racks	Storage Racks	Switch Racks
Type	POWER9	V100		Type	AC922	SSC (4 ESS GL4)	Mellanox IB EDR
Count	9,216 2 × 18 x 256	27,648 6 × 18 x 256		Count	256 Racks × 18 Nodes	40 Racks × 8 Servers	18 Racks
Peak FLOPS	9.96 PF	215.7 PF		Power	59 kW	38 kW
Peak AI FLOPS		3.456 EF			13 MW (Total System)

Summit has over 10 petabytes of memory.

Summit Total Memory
Type	DDR4	HBM2	NVMe
Node	512 GiB	96 GiB	1.6 GB
Summit	2.53 PiB	475 TiB	7.37 PB

Architecture

System

Weighing over 340 tons, Summit takes up 5,600 sq. ft. of floor space at Oak Ridge National Laboratory. Summit consists of 256 compute racks, 40 storage racks, 18 switching director racks, and 4 infrastructure racks. Servers are linked via Mellanox IB EDR interconnect in a three-level non-blocking fat-tree topology.

Compute Rack

Each of Summit's 256 Compute Racks consists of 18 Compute Nodes along with a Mellanox IB EDR for a non-blocking fat-tree interconnect topology (actually appears to be pruned 3-level fat-trees). With 18 nodes, each rack has 9 TiB of DDR4 memory and another 1.7 TiB of HBM2 memory for a total of 10.7 TiB of memory. A rack has a 59 kW max power and a total of 864 TF/s of peak compute power (ORNL reports 775 TF/s).

Compute Node

The basic compute node is the Power Systems AC922 (Accelerated Computing), formerly codename Witherspoon. The AC9222 comes in a 19-inch 2U rack-mount case.

Each node has two 2200W power supplies, 4 PCIe Gen 4 slots, and a BMC card. There are two 22-core POWER9 processors per node, each with 8 DIMMs. For the Summit supercomputer, there are 8 32-GiB DDR4-2666 DIMMs for a total of 256 GiB and 170.7 GB/s of aggregated memory bandwidth per socket. There are three V100 GPUs per POWER9 socket. Those use the SXM2 form factor and come with 16 GiB of HBM2 memory for a total of 48 GiB of HBM2 and 2.7 TBps of aggregated bandwidth per socket.