sPHENIX is a new detector at RHIC.

[Ross Corliss <ross.corliss AT stonybrook.edu>]

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!AY1IkA7FC-cNYEPZqc4zWrNyh84kwdGYwqSl4isD-VX-rHVa1L4A9B0PSRF74yYi3kXcQR0AQtavBcwOPcq4enIvlnYXC1xDLs0$
 

> 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!AY1IkA7FC-cNYEPZqc4zWrNyh84kwdGYwqSl4isD-VX-rHVa1L4A9B0PSRF74yYi3kXcQR0AQtavBcwOPcq4enIvlnYXW0wzipg$
>>   
>> <https://urldefense.com/v3/__https://agenda.infn.it/event/28874/contributions/169210/__;!!P4SdNyxKAPE!HOjf-fN0HvR_ZMzbk6AZHmhZWHNGkfVDRTWXzeaMUH5cToXrNDht4HVvHfG3hFtfxRIteJAtIzHm0zt3PVyFNHpi1G3TLAwlQzk$>
>>  (11:30 AM local conference time)
>> I welcome any comments or suggestions you may have, and I'll second 
>> Murad's earlier thanks to all the speakers who have uploaded their slides 
>> for the collaboration meeting and other recent reports.
>> Gratefully,
>> -Ross
>> ==========
>> Dr. Ross Corliss
>> Research Assistant Professor
>> Center for Frontiers in Nuclear Science
>> Stony Brook University
>> virtual office: 
>> https://urldefense.com/v3/__https://stonybrook.zoom.us/my/rossoffice?pwd=ZmZ2SlRIMVFvUUJwbUkyOVNVTmE5QT09__;!!P4SdNyxKAPE!AY1IkA7FC-cNYEPZqc4zWrNyh84kwdGYwqSl4isD-VX-rHVa1L4A9B0PSRF74yYi3kXcQR0AQtavBcwOPcq4enIvlnYXC1xDLs0$
>>   
>> <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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