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QsNet III An HPC Interconnect

for PetaScale Systems

Duncan Roweth, Quadrics LtdISC08 Dresden June 2008

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Quadrics Background

Develops interconnect products for the HPC market HPC Linux systems AlphaServer SC systems

Quadrics is owned by the Finmeccanica group

Quadrics will be 12 years old in July

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Interconnect Network QsNet

QsNet IIINetwork Multi-stage switch network Evolution of the QsNet II design Increased use of commodity hardware Increasing support for standard

software

QsNet IIIComponents ASICs Elan5 and Elite5 Adapters, switches, cables Firmware, drivers, libraries Diagnostics, documentation

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Fabric

Bridge

x8

PLL

EEPROM ClocksPCIe16 Lanes

Host I/F

TLB

Cmd Launch

PCIe

SERDES

Local Functions

Buffer Manager

Object Cache Tags

Free List

Local Memory

Ext i/f SDRAM i/f

External cache

ExternalDDRII

16K x 8 x 8 banks = 1MB ECC RAM

CX4/QSNet III

Link

CX4/QSNet III

Link

Packet Engine16K inst cache9K data buffers

Packet Engine16K inst cache9K data buffers

Packet Engine16K inst cache9K data buffers

Packet Engine16K inst cache9K data buffers

Packet Engine16K inst cache9K data buffers

Packet Engine16K inst cache9K data buffers

Packet Engine16K inst cache9K data buffers

Elan5 Adapter

Elan5 Adapter Overview

2 25 Gbit/s QsNet III links PCIe, PCIe2 host interface Multiple packet engines 512KB of high bandwidth on

chip local memory SDRAM interface to optional

local memory Buffer manager, object

cache

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QsNet III Adapter Overview

QM700 PCIe x16 128MB adapter memory 2 QSFP links

Half height low profile

Adapters variants PCIe Gen2 Blade formats 10Gbit/s Ethernet 10GBase-CX4

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QsNet III Adaptive Routing

Packet by packet dynamic routing Single cycle routing decision

Selects route based on Link state, errors etc

Number of pending acks High radix switches 2 routing decisions for 2048 nodes

More flexible than QsNet II

Operates on groups of links

Can adaptively route up or down

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Bandwidth scalability 1024 nodes

Bandwidth achievedwhen 1024 nodes allcommunicate at thesame time

QsNetII

provides betteraverage bandwidthand much narrowerspread in best to worstcase performance

System Interconnect Min Max Average

Atlas Infiniband 95 762 263

Thunder QsNet II 248 403 369

Data from Lawrence Livermore National Lab, published at the Sonoma OpenFabrics workshop June 2007

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QsNet III Federated Network Switches

Node switch chassis 128 links up 128 down

Same chassis provides multiple

top switch configurations: 64 4 512-way systems 32 8 1024-way systems 16 16 2048-way systems 8 32 4096-way systems

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QsNet III Network 4096 way

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QsNet IIIcables

QSFP connectors throughout Optical cables (e.g.Luxtera), 5-300m

PVDF Plenum rated LSZH available as an option

Active copper cables (Gore), 8-20m Copper cables (Gore) 1-10m No longer Quadrics proprietary

Bit error rates are a big issue at 5 Gbpsand above Optical cables between switches Short copper cables from nodes

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QsNet III for HP BladeSystem

Elite5 switch moduleFull bandwidth16 links to the blades (via backplane)16 links to back of the module

Elan5 mezzanine adapter2 QsNet linksPCI-E x8 (initially)

128 MB of memory

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2048-way QsNet III BladeSystem Network

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Building a 16K node system in 2009/10

Single water cooled rack willprovide 1000-2000 standardcores ~12-25 TF.

8 Blade switches per rack Connect 128 of these racks

with 1024-way top switches

Single fibre cable per node -for full bi-section bandwidth.

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QsNet III Fault Tolerance

All of the QsNet II Features CRCs on every packet Automatic retransmission Adaptive routing avoids failed links Redundant routes Redundant, hot plugable, PSUs and fans

+ Full line rate testing of each link as it comes up Switches generate CRPAT, CJPAT or PRBS packets Links are only added to the route tables when they are (a)

up, (b) connect to the right place, and (c) can transfer datawithout error.

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Software Model Firmware & Drivers

Base firmware in the ROMs Firmware modules loadable with the device driver

Elan, OpenFabrics, 10GE Ethernet,

Kernel modules elan5, elan, rms

Device dependent library (libelan5) Device independent library (libelan)

User libraries

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Point-to-point messagepassing

One-sided put/get Transparent rail striping

Optimised collectives Locks and atomics ops Global memory allocation

Software Model Elan Libraries

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Focus on the most demanding HPC applications Delivers large system scalability

All nodes achieve host adapter bandwidth at the same time Minimal spread between best and worst case performance

Low and uniform latency Highly optimised collectives

Single supplier of interconnect hardware, software, support Stability of our products

Track record of delivering production systems European company

Why Quadrics?