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PHENIX DAQ RATES

PHENIX DAQ RATES. RHIC Data Rates at Design Luminosity. Design Luminosities. Au-Au: L = 2 x 10 26 cm -2 s -1 p-p: L = 2 x 10 32 cm -2 s -1. PHENIX Max <rate> = 25 kHz Every FEM must send in 40 us. Since we multiplex 2, that limit is 12 kHz and 80 us.

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PHENIX DAQ RATES

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  1. PHENIX DAQ RATES

  2. RHIC Data Rates at Design Luminosity Design Luminosities Au-Au: L = 2 x 1026 cm-2 s-1 p-p: L = 2 x 1032 cm-2 s-1 • PHENIX Max <rate> = 25 kHz • Every FEM must send in 40 us. • Since we multiplex 2, that limit is 12 kHz and 80 us. • For Au-Au, Level-1 rate is ~1400 Hz - we sample every event in the level-2. • For p-p, the interaction rate is 10MHz - need very good level-1 rejection.

  3. Run Segments (“borrowed” from Bill’s RBUP) • Assumptions: • A total period of 25 weeks for beam availability • RHIC duty factor = 50% • PHENIX duty factor = 50% • Collision region rms = 20 cm. • All running at • Au-Au segment of 17 weeks: • First 7 weeks: • RHIC: commissioning from ~10% to 100% of design luminosity • PHENIX: Commissioning, calibrating, start of data-taking • Last 10 weeks: • Running at ~100% of design luminosity (2 x 1026 cm-2 s-1) • 300 mb-1 (possibly 600) of integrated luminosity recorded • p-p segment of 8 weeks • 2 weeks to commission collisions • 1 week to commission polarization (> ~50%) • 5 weeks of polarized running at 5 x 1030 cm-2 s-1 • 3.5 pb-1 of integrated luminosity recorded:

  4. Data Type Size (bytes) Data Type Size (bytes) UnSuppressed 2.93 x 10^6 Au-Au Central 4.02 x 10^5 10% occ Au-Au mbias 1.61 x 10^5 2.5% occ Au-Au mbias 1.26 x 10^5 2.5% occ, min fem header p-p mbias 4.30 x 10^4 0% occupancy min fem header Packet > 22 x 10^3 Header FEM Header 53.2 x 10^3 Minimal FEM 18.1 x 10^3 Header (clk, evt, summary) Data Volumes http://www.nevis.columbia.edu/~nagle/Trigger/phenix_data_volume2.htm Overhead • Is the minimal FEM header really “the” mininal? • Packet and FEM headers can be dropped from empty packets, but not from non-empty ones • We are currently running with all headers and packets...

  5. DSPs 1-4 Reads in FEM data, 0-suppress 20 MB/s Link Port Process Data DSP 5 (1 per DCB) PARTITIONER 160 MB/s Joins Data, further processing High Speed Transfer to SEB Joins Data, further processing Joins Data, further processing (40 MHz) Token Passing Bus PHENIX Hardware Throughput FEM LEVEL-1 Must be able to make L1 decision in 40 beam crossings (GL1 + LL1) Spews out data at 25 kHz* 40 MHz DC, TEC 20 MHz all else. (ie, 160 or 80 MB/s) DCM FPGA fiber LVDS CABLE to Event Builder *EMC needs short format FPGA, TOF needs extra controllers to get < 40us output time.

  6. Assemble Events, Run Level 2 Trigger HPSS 20 MB/s 28? ATPs (NT 4) PHENIX Hardware Throughput Event Builder Buffer Data from DCM’s 10 Gbit/s aggregate, 5 each way LVDS CABLE (from PAR) JSEB Input Card (PCI, 132 MB/s) 155 Mbit/s NIC 155 Mbit/s NIC Fore ASX-1000 ATM Switch 26? SEBs (NT 4) 28? x 100Mbit ethernet • Each SEB can write out at 155 Mbit/s, so max rate is (155Mbit/s - overhead)/event size • 20 MB/s sustained max overall output rate set by HPSS • 30-40 into the buffer boxes is • instantaneous rate. 30-40? MB/s RAID Dual Buffer Storage in RAID Arrays running on Linux Box (one writes to HPSS, one reads from ATPs) Buffer Boxes

  7. Current Status, 2001-08-18 MVD Largest Granule Event Rate ~ 600 Hz Event Size = 120 kBytes

  8. Some Personal Thoughts... • For the Au-Au running, we want to be at 1400 Hz, and it would be even better to get to 2100 Hz if we want the coherent peripheral • program to succeed. • We are currently somewhere around 600 Hz, but we’re still working on it. • Given the limit of 155 MBits/s per SEB due to the ATM NIC, the Level 1 limit is set by the DC - at 2.5% occ, event size is 26.3 kB, so 15 MB/26.3 kB => max rate of 1140 Hz. • If we go to minimal FEM headers, the DC size goes down to 21.8kB, or a max rate of ~1400 Hz. • If we want coherent peripheral, we’d need to split the DC granules. • Still a lot of work to do for p-p running, and none of it seems certain: minimize headers, drop packets, level-1 b • oards…

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