Eos is a 736-node Cray XC30 cluster with a total of 47.104 TB of memory. The processor is the Intel® Xeon® E5-2670. Eos uses Cray’s Aries interconnect in a network topology called Dragonfly. Aries provides a higher bandwidth and lower latency interconnect than Gemini. Support for I/O on Eos is provided by (16) I/O service nodes. The system has (2) external login nodes.
The compute nodes are organized in blades. Each blade contains (4) nodes connected to a single Aries interconnect. Every node has (64) GB of DDR3 SDRAM and (2) sockets with (8) physical cores each. Intel’s Hyper-threading (HT) technology allows each physical core to work as two logical cores so each node can functions as if it has (32) cores. Each of the two logical cores can store a program state, but they share most of their execution resources. Each application should be tested to see how HT impacts performance before HT is used. The best candidates for a performance boost with HT are codes that are heavily memory-bound. The default setting on Eos is to execute without HT, so users must invoke HT with the -j2 option to aprun.
In total, the Eos compute partition contains 11,776 traditional processor cores (23,553 logical cores with Intel Hyper-Threading enabled), and 47.6 TB of memory.
For more information about Eos, please see the Eos User Guide located at https://www.olcf.ornl.gov/support/system-user-guides/eos-user-guide/.