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Correlator Backend System

Learn about the major components and processing of a high-speed correlator backend system, including data rates, limiting factors, interface connections, development schedule, and connection modes.

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Correlator Backend System

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  1. Correlator Backend System Overview Tom Morgan, NRAO Correlator Backend System Overview

  2. Major Systems Correlator M & C Backend e2e Correlator Backend System Overview

  3. Backend Components Correlator Backend System Overview

  4. Backend Processing • Verify Correlator Output • Assemble Lag Sets from Lag Frames • Apply Normalizations and Corrections • FFT • Integrate • Noise Reduction/Excision Correlator Backend System Overview

  5. Initial Data Rates • 64 Correlator Chips per Baseline Board (16 Sub-bands x 4 Polarization Products) x 2048 Lags x 8 Bytes per Lag = 1 Mbyte per CC per Dump • 0.1 sec Dump Interval => 10 Mbytes/sec per Baseline Board • 160 Baseline Boards => 1.6 Gbytes/sec Aggregate Sustained Input Rate • 64:1 Reduction (6.4 sec Integration Time) on Backend => 25 Mbytes /sec Aggregate Sustained Output Rate Correlator Backend System Overview

  6. Data Rate Limiting Factors • Connection Technology and Switch Speeds • Memory and Disk Storage Capacities • Processor Speeds • Archive Size and Filling Rates • Ultimately a $ Limitation Correlator Backend System Overview

  7. Correlator to Backend Interface • 160 (27-32 Antennas) Minimum to 336 (48 Antennas) Correlator Connections • ~50 Backend Connections • Initial Maximum Aggregate Transfer Rate of 1.6 Gbytes/sec • Gbit/sec Switch Correlator Backend System Overview

  8. Backend to e2e Interface • Initial Maximum Aggregate Transfer Rate of 25 Mbytes/sec • ~ 50 Backend Connections • Formatted as AIPS++ Measurement Sets • Avoid Inter-processor Data Movement on the Backend • Minimize Overheads on the Backend • Backend has Provision for Backup Storage of Output on Disk Correlator Backend System Overview

  9. e2e Connection Modes • Network Based Message Passing • Channel Based I/O • Backend Driven • e2e Driven Correlator Backend System Overview

  10. Message Passing • Backend Output Transfer via Network Packets • High Speed Ethernet Correlator Backend System Overview

  11. Channel I/O • Backend Output Data Transfer via Direct File Read/Write or Memory Copy • Fiber Channel, SCSI … Correlator Backend System Overview

  12. Backend Driven • Backend System Runs Software that does Transfers • If Message Passing: Backend Sends Data to an e2e Based Process and Retains a Copy until Receipt is Acknowledged • If Channel I/O: Backend does Direct FileWrites into the Archive Correlator Backend System Overview

  13. e2e Driven • e2e System Runs Software that does Transfers • If Message Passing: e2e Runs Processes on Backend Nodes and Accesses Files or Memory for Data • If Channel I/O: e2e does File Read/Write or Memory Copy from Either End Correlator Backend System Overview

  14. Development Schedule • 2Q 2002 – 4 Node Test Cluster • 3Q 2002 – 8+ Node Cluster • 4Q 2002 – Functional Prototype • 3Q 2003 – Activate e2e Connection • 4Q 2003 – Full Functionality • 3Q 2004 – First Prototype Correlator Boards • 4Q 2004 – Earliest BE Connect to Correlator Hardware Correlator Backend System Overview

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