QsNetIII Network –Multi-stage switch network –Evolution of the QsNetIIdesign –Increased use of commodity hardware –Increasing support for standard software •QsNetIII Components –ASICs Elan5 and Elite5 –Adapters, switches, cables –Firmware, drivers, libraries –Diagnostics, documentation

1. QsNetIII An HPC Interconnect
for PetaScale Systems
Duncan Roweth, Quadrics Ltd
ISC08 Dresden June 2008

2. 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

3. Interconnect Network – QsNet
• QsNetIII Network • QsNetIII Components
– –
Multi-stage switch network ASICs Elan5 and Elite5
– –
Evolution of the QsNetII design Adapters, switches, cables
– –
Increased use of commodity hardware Firmware, drivers, libraries
– –
Increasing support for standard Diagnostics, documentation
software

4. Elan5 Adapter Overview
CX4/ CX4/
• QSNetIII QSNetIII
QsNetIII
2 × 25 Gbit/s links
• PCIe, PCIe2 host interface Elan5 Adapter
Link Link
• Multiple packet engines Packet Engine Packet Engine Packet Engine Packet Engine Packet Engine Packet Engine Packet Engine
16K inst cache 16K inst cache 16K inst cache 16K inst cache 16K inst cache 16K inst cache 16K inst cache
• 512KB of high bandwidth on 9K data buffers 9K data buffers 9K data buffers 9K data buffers 9K data buffers 9K data buffers 9K data buffers
chip local memory Fabric
• SDRAM interface to optional x8
local memory Bridge
Host I/F Local Memory Local Functions
Object Cache Tags
TLB
• Buffer manager, object
Buffer Manager External cache
Cmd Launch
SDRAM i/f Ext i/f
Free List
PCIe
16K x 8 x 8 banks = 1MB ECC RAM PLL
cache
SERDES
External EEPROM Clocks
PCIe
DDRII
16 Lanes

5. QsNetIII 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

6. Elite5 - Overview
• Physical layer DDR XAUI
– 4 x 6.25Gbit/s (2.5Gbytes/s)
in each direction
• 32-way crosspoint router
• 32 virtual channels per link
• Fat tree or mesh topologies
• Adaptive routing
• Broadcast & barrier support
• Memory mapped stats & error
counters accessed via control
network

7. QsNetIII 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 QsNetII
– Operates on groups of links
– Can adaptively route up or down

8. Bandwidth scalability – 1024 nodes
• Bandwidth achieved
when 1024 nodes all
communicate at the
same time
• QsNetII provides better
average bandwidth
and much narrower
spread in best to worst
case performance
System Interconnect Min Max Average
Atlas Infiniband 95 762 263
QsNetII
Thunder 248 403 369
Data from Lawrence Livermore National Lab, published at the Sonoma OpenFabrics workshop June 2007

9. QsNetIII Device Overview
Elan Elite
Manufacturing partner LSI/TSMC G90 process
Semi custom ASICs, 500MHz system clock
High performance BGA package
672 pin 982 pin
17W 18W

10. QsNetIII – 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

11. QsNetIII Network 4096–way

12. QsNetIII cables
• 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 Gbps
and above
– Optical cables between switches
– Short copper cables from nodes

13. QsNetIII for HP BladeSystem
Elan5 mezzanine adapter
2 QsNet links Elite5 switch module
PCI-E x8 (initially) Full bandwidth
128 MB of memory 16 links to the blades (via backplane)
16 links to back of the module

14. 2048-way QsNetIII BladeSystem Network

15. Building a 16K node system in 2009/10
• Single water cooled rack will • 8 Blade switches per rack
provide 1000-2000 standard • Connect 128 of these racks
cores ~12-25 TF. with 1024-way top switches
• Single fibre cable per node -
for full bi-section bandwidth.

16. QsNetIII Fault Tolerance
• All of the QsNetII 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 data
without error.

17. 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

18. Software Model – Elan Libraries
• Point-to-point message • Optimised collectives
passing • Locks and atomics ops
• One-sided put/get • Global memory allocation
• Transparent rail striping

19. Why Quadrics?
• 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