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Increase the event rate into Level 3 Increase the event rate onto storage

Possible DAQ Upgrades DAQ1k… DAQ2k… DAQ10k!? Tonko Ljubi čić STAR/BNL (for the “3L Group” — Landgraf, LeVine & Ljubi čić ) ( Lange would fit nicely too, ). Increase the event rate into Level 3 Increase the event rate onto storage … but make it cheap (unlikely)

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Increase the event rate into Level 3 Increase the event rate onto storage

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  1. Possible DAQ UpgradesDAQ1k… DAQ2k… DAQ10k!?Tonko LjubičićSTAR/BNL(for the “3L Group” — Landgraf, LeVine & Ljubičić)(Lange would fit nicely too, ) • Increase the event rate into Level 3 • Increase the event rate onto storage … but make it cheap (unlikely) … and make it simple (unlikely) … and do it without additional manpower (ridiculous) … and do it while STAR is taking data (problematic)

  2. Assumptions… • We have the TPC (or similar) i.e. a tracking device with many channels • We want a Level 3 trigger (based upon tracks) • We have a good cluster finder so we save only the 2D hitpoints • The final storage (tapes) is under RCF’s control • Assumed Requirements: • At least1000 Hz Level 3 rate (central, Au+Au) • At least100 Hz storage rate (central, Au+Au)

  3. DAQ Components • Event Builder and event buffer • Level 3 CPU farm • DAQ frontend (Cluster Finder, Formatter) • Detector Frontend (FEE) • Network interconnect: • Between DAQ frontend, L3, EVB • Between FEE and DAQ frontend

  4. DAQ Components (cont’d)(current) • EVB: 1 Sun, 70 MB/s, 700 GB buffer  10 Hz central AuAu raw, 50 Hz clusters only • L3: 48 500 MHz Alphas  50 Hz central AuAu • DAQ RB: 144X3 slow I960CPUs  50 Hz central AuAu • TPC FEE:100 Hz • Network: • Main: Myrinet, 100 MB/s/link • FEEDAQ: 1.25 Gb/s 100 evts/s

  5. Upgrades (EVB) • Cluster of Linux CPUs connected via Gigabit ethernet switch to RCF • Each has: • Large (and cheap) disk buffers (i.e. 4 X 120 GB IDE) • 512 MB memory (not that much) • 1 Gigabit Ethernet card (cheap) • 1 Myrinet card (for internal DAQ) (1 k$) • 1 CPU of any slow variety (not CPU-intensive) • Good, fast motherboard (I/O intensive) • Need about 5-10 of them • Advantages: • Scalability – adding more nodes increases rates linearly • Paralellism is simple – round robin on an event-by-event basis, all nodes are equal • Robustness – all are the same, trivial automatic recovery in case of failure • Cost – IDE disks are soooo much cheaper than SCSI • Cost: 4 k$ per cluster (nicely equipped). Now! • Compare to current 50 k$ for a single Sun workstation: for the cost of one Sun we get 10 X (!) the throughput!

  6. Upgrades (TPC FEE) • ALICE developed a FEE chip for their own TPC (ALTRO) • 8 channel analog/digital hybrid with ADCs and DSP on chip • pedestal subtraction, gain correction, baseline restoration, zero-suppression and event buffering (8 buffers) on chip • (up to) 20 MHz sampling clock • Decoupled readout clock of (up to) 40 MHz • Available now (?) • Needs more evaluation but looks promising! • Expect more details from the Berkeley guys in the near future (Bieser, Crawford)

  7. Upgrades (DAQ frontend) • Inputs data from detector FEE, finds clusters, formats them, calculates pedestals, buffers data, ships to L3/EVB, etc. – versatile • Works on a M X N (2D) plaque suitable for most detectors (i.e. TPC padrow is 182 X 512, SVT is 240 X 128, etc.) – “detector blind” • Current example: • Intel I960HD CPU, 66 MHz internal, 33 MHz external bus takes ~ 7 ms for a central Au+Au event per padrow  need speedup of ~10 X (but hope for more, ) • Possible choices: • DSPs (“easy” to program; many, many to choose from) • FPGAs (tough to program, fast!, many to choose from) • Embedded FPGA cores or hybrids (i.e. Xilinx Virtex II Pro) • Combination of both FPGA & CPU • Versatile – many have fast links (i.e. 3.25 Gb/s !) on chip! • Extremely complex! • Expensive! (at least now…) • A lot of R&D: • Evaluate possible hardware choices (above) • Adapt the cluster finder software to the different hardware • Need very specific manpower – possible cooperation with Instrumentation Division • Very critical item – need to start work NOW! (R&D funding)

  8. DAQ Interconnects • Complex issue depends on: • Where will the Cluster Finder be? On the detector? In the DAQ room? • What is done in FEE vs. Cluster Finder? Does FEE zero-suppress (ala ALICE FEE) or it is left to the DAQ frontend (like now)? • Data aggregation and scheduling? How does one pack this data? Multiplexing scheme? Data routing? • How many fibers one needs? At which speed? Which topology? • Does one use commercially available switches/protocols (i.e. Gigabit, 10 Gb???) or use custom built (like we do now)? • One needs to ship a Sector’s worth of data to a single L3 Node – how? Which network? Which topology? • Cost !? • Need to start thinking NOW!

  9. Level 3 (tracking) • This is tough: • Currently takes 40 ms/sector with a pretty fast (500 MHz 21264 Alpha) CPU  need to speed up at least 50 times! • How to get 50 X (some ideas): • Faster CPU in 6 years (~ 4X) • Concentrate on primary tracks (~2 X) • Know the vertex (~2 X). Need vertex detector!!! • Tune the code (~ 2 X) • Only tracks that exit the volume i.e. pass trough the last padrow in the TPC (implied rapidity-Pt cut) (~2 X) • Use as seeds track hits in other detectors (EMC? TOFRPC?) (~ 2X) • Parallelize, parallelize, parallelize! • i.e. each CPU node is a 4way SMP with each CPU working on one track in parallel (~4 X) • Could be done!(With a lot of magic wand waiving…) • Cost!? Assume 4 X 4way SMP per sector @ 24 sectors that’s 96 4way SMP machines. @10 k$ machine that’s ~ 1 M$. Doable.

  10. Level 3 (cont’d) • How to reduce cost and make it sweeter? • Let’s look at Offline vs. Level 3 CPU farms similarities: • Both need super fast CPUs • A lot of them! • Offline needs a fast connection to the data source (i.e. HPSS tapes) but Level 3 already has (or can easily be made to have) a connection to HPSS! • Differences: • Offline needs disks and a lot of memory – L3 doesn’t • Offline needs different code structures and perhaps OS setup • Skin Changing Local Grid • Level 3 nodes “become” reconstruction nodes when not in use in DAQ(“change skin”) • Level 3 generally boots diskless (for L3) and this system is under complete control of the L3 Group. L3 code doesn’t even need to know that there are disks in the node! • Offline needs disks and all the code (kernel/OS/reconstruction) images on those disks are under complete control of Offline. • Switch from the Level 3 “skin” to Reconstruction is done via a reboot command with an appropriate parameter (i.e. “boot –l3” or “boot –offl”). (The simplest, cleanest but slowest way) • Advantages: • Major cost saving • Disadvantages: • Can’t run the whole system at the same time (but one could run certain partitions depending on the required load!)

  11. Summary • EVB rates no problem (up to 500 MB/s) for STAR-DAQ however the RCF side is a different issue (see M. Messer’s talk) • Detector FEE + DAQ Frontend + Level 3 needs a complete rehaul and we must start from scratch • If we maintain any of the existing systems we can not go above 50 Hz • 1000 kHz (or more) into Level 3 is doable but a lot of work needs to be done to optimize it • We need to know what are we looking for in L3 since a completely general and exhaustive tracking will probably not be possible • Most of the Level 3 cost could be shared between Offline Reconstruction if we use the Skin Changing scheme

  12. Conclusion • Doable • Need R&D effort (funding, manpower) immediately for: • TPC FEE overhaul • DAQ frontend studies; hardware and software adaptations • Interconnect/network studies for the FEEDAQ data transfer as well as DAQL3 • Need strong support from the collaboration – the effort needed is too large to be done in “our spare time” • We should change the name to SuperSTAR

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