XK Series

Cray XK Series Supercomputers

Bringing Cray’s trademark reliability, flexibility and scalability to the many-core HPC environment

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Cray® XK™ Series Supercomputers

The Cray® XK7™ supercomputer combines Cray’s proven Gemini interconnect, AMD's leading multicore scalar processors and NVIDIA’s powerful many-core GPU processors to create a true, productive hybrid supercomputer.

Capable of scaling to 500,000 scalar processors and 50 petaflops of hybrid peak performance, every aspect of the Cray XK7 system — from its resiliency features to its scalability-boosting technologies — has been engineered to meet science’s real-world demands. And with the expertise of the industry’s only company singularly focused on high performance computing behind it, the Cray XK7 supercomputer brings Cray’s trademark reliability, flexibility and scalability to the many-core HPC environment.

Featured Resources

Four Large-Scale Science Applications Sustain 1+ Petaflops on Cray XE/XK System “Blue Waters”

Working with Cray on optimizations, researchers ran four of the applications (VPIC, PPM, QMPACK and SPECFEM3D_GLOBE) above 1 petaflops of sustained performance.

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Cray® XK7™: Scalable Many-Core Performance

Adaptive Hybrid Computing

The Cray® XK7™ compute node combines AMD's 16-core Opteron™ 6200 Series processor and the NVIDIA® Tesla® K20 GPU Accelerator to create a hybrid unit with the intra-node scalability, power-efficiency of acceleration and flexibility to run applications with either scalar or accelerator components. This compute unit, combined with the excellent inter-node scalability of Cray’s Gemini interconnect, creates a system geared for any computing challenge.

Production Reliability

Integrated Hardware Supervisory System

Cray's Hardware Supervisory System (HSS) integrates hardware and software components to provide system monitoring, fault identification and recovery. An independent system with its own control processors and supervisory network, the HSS monitors and manages all major hardware and software components in the Cray XK7 supercomputer. In addition to providing recovery services in the event of a hardware or software failure, HSS controls power-up, power-down and boot sequences, manages the interconnect, reroutes around failed interconnect links, and displays the machine state to the system administrator. 

Cray XK7 System Resiliency

The Gemini interconnect is designed for large systems in which failures are to be expected and applications must run to successful completion in the presence of errors. Gemini uses error correcting code (ECC) to protect major memories and data paths within the device. In addition, the Cray Linux Environment (CLE) features NodeKARE™ (Node Knowledge and Reconfiguration). If a program terminates abnormally, NodeKARE automatically runs diagnostics on all involved compute nodes and removes any unhealthy ones from the compute pool. Subsequent jobs are allocated only to healthy nodes and run reliably to completion. The XK7 supercomputer’s Lustre® file system can be configured with object storage target failover and metadata server failover. 

Adaptive Supercomputing 

Extreme Scale and Cluster Compatibility

The Cray XK7 system provides complete workload flexibility — a single machine can run both a highly scalable custom workload and industry-standard ISV workload. CLE accomplishes this through Cluster Compatibility Mode (CCM). CCM allows immediate compatibility with Linux/x86 versions of ISV software — without recompilation or relinking — and allows for the use of various versions of MPI (such as, MPICH and Platform MPI™). The service is dynamic and available on an individual job basis.

Support for Other File System and Data Management Services

You can select the Lustre parallel file system or another option including connecting to an existing parallel file system. The Cray Data Virtualization Service allows for the projection of various other file systems (including NFS, GPFS™, Panasas® and StorNext®) to the compute and login nodes on the Cray XK7 system. Cray can also provide solutions for backup, archiving and data lifecycle management.

Power Efficiency

Many-core processing is the key to ultimate energy efficiency. Applications using the Cray XK7 GPU processors will experience industry-leading energy efficiency when measured for real application workloads. Combined with our standard air- or liquid-cooled high-efficiency cabinet and optional ECOphlex™ technology, the Cray XK7 system can reduce cooling costs and increase flexibility in datacenter design.

Software for the Cray® XK7™ System

The Cray® XK7™ supercomputer supports a full range of powerful scalar tools, libraries, compilers, operating system and third-party software. 

Programming Environment

Each Cray XK7 system includes a fully integrated Cray programming environment with tools designed to maximize programmer productivity and application scalability and performance. The XK7 supercomputer can use a variety of high performance Fortran, C and C++ compilers and libraries for both x86 and GPU workloads. Available compilers include GPU-enabled PGI, CAPS, PathScale and the Cray Compiling Environment (CCE) for x86 with support for the ISO Fortran standard (2008) including parallel programming using coarrays, C/C++ and UPC. High performance-optimized math libraries include BLAS, FFTs, LAPACK, ScaLAPACK, SuperLU and Cray Scientific and Math Libraries.

Programming Models

Supported parallel programming models include MPI, CUDA, Cray SHMEM, UPC, Coarray Fortran, OpenMP and OpenACC. The MPI implementation is compliant with the MPI 2.0 standard and is optimized to take advantage of the Gemini interconnect. Cray’s performance and analysis toolkit, CrayPAT™, allows users to analyze resource utilization throughout their code at scale and eliminate bottleneck and load imbalance issues. In addition, the Gemini interconnect has direct hardware support for partitioned global address space (PGAS) programming models including Unified Parallel C (UPC), Co-Array Fortran and Chapel.

Scalable Software

The Cray XK7 system includes the latest Cray Linux Environment (CLE), a suite of high performance software including a SUSE® Linux®-based operating system designed to scale efficiently and run large, complex applications. With highly scalable applications, Compute Node Linux (CNL) runs in Extreme Scalability Mode, ensuring operating system services do not interfere with application scalability. Additionally, the Cray XK7 system provides for tightly integrated, industry-standard batch schedulers, compilers and debuggers.


Cray is a joint founding member of OpenACC, an organization that is driving a new directives-based open parallel programming standard enabling scientific and technical programmers to more easily leverage the performance optimization capabilities of hybrid CPU/GPU computing systems. Learn more by visiting www.OpenACC.org.

Product Brochures

Case Studies

Researchers Create Largest-Ever Storm Prediction Model to Simulate Hurricane Sandy Using ‘Blue Waters’ — NCSA’s Cray® XE6™ Supercomputer

The devastation caused by Hurricane Sandy and other super storms like it signals the need for further advances in the accuracy and reliability of numerical weather prediction. 

Cray System “Blue Waters” Helps Researchers Develop a Defense Against Damaging Space Weather

The solution — and the challenge — to coping with the effect of solar storms on Earth and its technological systems is forecasting space weather.

Using Cray System “Blue Waters,” Researchers Break the HIV Capsid Code and Open the Door to New Virus-Busting Therapies

Researchers have long sought to understand how the HIV capsid — a protein shell that protects the virus’s genetic material — is constructed.

Four Large-Scale Science Applications Sustain 1+ Petaflops on Cray XE/XK System “Blue Waters”

Working with Cray on optimizations, researchers ran four of the applications (VPIC, PPM, QMPACK and SPECFEM3D_GLOBE) above 1 petaflops of sustained performance.

Titan Simulates Earthquake Physics Necessary for Safer Building Design

Researchers conduct unprecedented study on GPUs of high-frequency shaking

GPUs and the Science of Smooth Ice Cream

Cray XK6 system helps scientists accelerate research into soft matter

Applications for Cray Systems

Tuning NAMD on the Cray XK6 "Titan" Supercomputer

With Cray support, the NAMD developers are optimizing their code on each new iteration of Cray hardware, achieving scaling to hundreds of thousands of cores.

Adaptive Computing: Moab HPC Suite for Cray

With Moab HPC Suite from Adaptive Computing, Cray users get the highest workload productivity and service levels from systems.

Allinea Development Tools for Cray Supercomputers

Leading corporations and research institutions across the world are using Allinea Software products, which set the standard for capability, performance and ease of use.

Altair PBS Professional for Cray

Altair has extensively re-architected PBS Professional for Cray users, collaborating closely with Cray to ensure tight, seamless integration.

Rogue Wave Products Engineered for Cray

Developers of applications for Cray platforms can leverage Rogue Wave tools and components to improve productivity and fully harness the power of the hardware.


OpenACC Programming for Cray Supercomputers

Parallel programming has never been this easy.

Frontier Scientists: A Cray Supercomputer Called Fish

For more information visit FrontierScientists.com

NVIDIA: Scientists use a Supercomputer to Improve Ice Cream

One of life's simple pleasures is so complicated that it takes a supercomputer to understand it.

Frontier Scientists: What's a FLOP?

Greg Newby, director of the Arctic Region Supercomputing Center at the University of Alaska, Fairbanks, and Per Nyberg, Cray Inc., define flops and update us on the future of supercomputing and computational science.

CUDACast #3 - Your First OpenACC Program

In this CUDACasts video, we'll see how to take an existing application and, using a few OpenACC directives, accelerate the computationally intensive loops on the GPU using the Portland Groupp's pgcc compiler.

OpenACC Basics

"Introduction to OpenACC and CUDA Programming on the Cray XK7 Platform," course organized by the Swiss National Supercomputing Centre (CSCS), Lugano, Switzerland, February 2013

An Introduction to OpenACC

OpenACC and CUDA Programming on the Cray XK7 Platform

Using the Cray Programming Environment

Introduction to OpenACC and CUDA Programming on the Cray XK7 Platform

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