sPHENIX is a new detector at RHIC.

[Martin Purschke <purschke AT bnl.gov>]

Hi Ross,

yes, that ping-pong scheme refers to file systems on each of the 
bufferboxes.

Best,
        Martin

On 7/3/22 15:46, Ross Corliss wrote:
> Dear Martin,
>
> Thank you for fleshing out the details for me.  I take it the two file 
> systems you refer to are identical pairs within each buffer box, and not the 
> HPSS vs SDCC distinction?  I will clarify this (and perhaps add a backup 
> slide to support).
>
> I will correct 100ns to 110ns, and rest assured that I will say a bit more 
> out loud than is written on the slide.
>
>
> -Ross
> ==========
> Dr. Ross Corliss
> Research Assistant Professor
> Center for Frontiers in Nuclear Science
> Stony Brook University
> virtual office:  
> https://urldefense.com/v3/__https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09__;!!P4SdNyxKAPE!FnRR__MLRobMWa9WoLiooTD_WLdoqxFiyqbtzXosExVRCOyepC0zGSkm4chx950n7db4og4e-1Ol-P_A_0QTF-Yfv5IJWg$
>
> > On Jul 3, 2022, at 3:35 PM, Martin Purschke via sPHENIX-l 
> > <sphenix-l AT lists.bnl.gov> wrote:
> >
> > Hi Ross,
> >
> > nice talk.
> >
> > Just a correction, slide 5 - "Buffer boxes fill during peak lumi, drain out at end of 
> > fill". Not technically correct. I would say "The buffer boxes level the incoming data 
> > rates and allow us to send the average, rather than the peak rates to HPSS."
> >
> > Some more background for questions: In principle it would be sufficient to operate the 
> > system as a "leaky bucket" where a variable rate of water flows in and a 
> > steady rate flows out. The differences in incoming rate is carried by the varying water 
> > level in the bucket (buffering).
> >
> > For technical reasons we write the data to one of two file systems. When the 
> > written-to one hits a high-water mark, we clear the other (that has meanwhile 
> > been transferred to HPSS), and switch their roles. In this way one is only 
> > written to and the other is only read from, which dramatically increases the 
> > throughput (minimizing the disks' head movements).
> >
> > Since our buffer depth is large enough that we can average over several 
> > stores (5-10) and their no-data fill time, and also cover breaks for 
> > accesses, and often no-data MD and APEX days, we can take  advantage of the 
> > significantly lower average data rate compared to the peak rates. The HPSS 
> > and SDCC transfers only need to be able to sustain that average rate (plus a 
> > bit of reserve).
> >
> > Slide 6
> > non-RHIC folks will wonder where the 100ns come from (which should actually be 110ns == 
> > 1 beam crossing). I would try to bring across that the acquisition window needs to 
> > cover ~118 crossings (those 13 us) to get the data just from the triggered-on crossing, 
> > and by extending the window by n additional crossings we increase the covered crossings 
> > by a factor of n. This small delta is the "almost for free" aspect.
> >
> > Hope it helps. Good luck with the talk.
> >
> >         Martin
> >
> > On 7/3/22 14:05, Ross Corliss via sPHENIX-l wrote:
> > > Dear All,
> > > I've posted draft slides for the sPHENIX data reconstruction talk at 
> > > https://indico.bnl.gov/event/16174/contributions/64794/attachments/41947/70236/sPHENIX.Data.Reco.ICHEP.2022.pdf
> > >  
> > > <https://indico.bnl.gov/event/16174/contributions/64794/attachments/41947/70236/sPHENIX.Data.Reco.ICHEP.2022.pdf>
> > > The time slot is 15 minutes, so I assume 12.5+2.5 for talk+questions.   It takes 
> > > place in the computing session on Friday, July 8: 
> > > https://urldefense.com/v3/__https://agenda.infn.it/event/28874/contributions/169210/__;!!P4SdNyxKAPE!FnRR__MLRobMWa9WoLiooTD_WLdoqxFiyqbtzXosExVRCOyepC0zGSkm4chx950n7db4og4e-1Ol-P_A_0QTF-bQT3M2ug$
> > >   
> > > <https://urldefense.com/v3/__https://agenda.infn.it/event/28874/contributions/169210/__;!!P4SdNyxKAPE!HOjf-fN0HvR_ZMzbk6AZHmhZWHNGkfVDRTWXzeaMUH5cToXrNDht4HVvHfG3hFtfxRIteJAtIzHm0zt3PVyFNHpi1G3TLAwlQzk$>
> > >  (11:30 AM local conference time)
> > > I welcome any comments or suggestions you may have, and I'll second Murad's 
> > > earlier thanks to all the speakers who have uploaded their slides for the 
> > > collaboration meeting and other recent reports.
> > > Gratefully,
> > > -Ross
> > > ==========
> > > Dr. Ross Corliss
> > > Research Assistant Professor
> > > Center for Frontiers in Nuclear Science
> > > Stony Brook University
> > > virtual office: 
> > > https://urldefense.com/v3/__https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09__;!!P4SdNyxKAPE!FnRR__MLRobMWa9WoLiooTD_WLdoqxFiyqbtzXosExVRCOyepC0zGSkm4chx950n7db4og4e-1Ol-P_A_0QTF-Yfv5IJWg$
> > >   
> > > <https://urldefense.com/v3/__https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09__;!!P4SdNyxKAPE!HOjf-fN0HvR_ZMzbk6AZHmhZWHNGkfVDRTWXzeaMUH5cToXrNDht4HVvHfG3hFtfxRIteJAtIzHm0zt3PVyFNHpi1G3To4rbY1U$>
> > > _______________________________________________
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> >
> >
> > --
> > Martin L. Purschke, Ph.D.        ;   purschke AT bnl.gov
> >                                  ;   http://www.phenix.bnl.gov/~purschke
> >                                  ;
> > Brookhaven National Laboratory   ;   phone: +1-631-344-5244
> > Physics Department Bldg 510 C    ;   fax:   +1-631-344-3253
> > Upton, NY 11973-5000             ;   skype: mpurschke
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--
Martin L. Purschke, Ph.D.        ;   purschke AT bnl.gov
                                 ;   http://www.phenix.bnl.gov/~purschke
                                 ;
Brookhaven National Laboratory   ;   phone: +1-631-344-5244
Physics Department Bldg 510 C    ;   fax:   +1-631-344-3253
Upton, NY 11973-5000             ;   skype: mpurschke
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