LHC experiments Requirements and Concepts ALICE

DAQ 2000 workshop, Lyon, 20DAQ 2000 workshop, Lyon, 20thth October 2000 October 2000R.Divià, CERN/ALICER.Divià, CERN/ALICE 1

LHC experimentsLHC experiments

Requirements and Requirements and

ConceptsConcepts

ALICEALICE



LEP in 1989...LEP in 1989...


… … and in 2000and in 2000





OutlineOutline ALICE general descriptionALICE general description RequirementsRequirements ArchitectureArchitecture SoftwareSoftware Data ChallengesData Challenges


Two running modesTwo running modes

Dr Jekyll…Dr Jekyll… Pb-Pb collisionsPb-Pb collisions general-purpose heavy ion experimentgeneral-purpose heavy ion experiment

… … and Mr Hydeand Mr Hyde pp beampp beam large cross-section pp processeslarge cross-section pp processes


ALICE data ratesALICE data rates

1 month (101 month (1066 s) s)

11

MinimumMinimumBiasBias

20201 - 871 - 87

CentralCentral

202067 - 8767 - 87

DielectronsDielectrons

20020067 - 8767 - 87

DimuonDimuon

6706700.7 - 2.40.7 - 2.4

24.524.5

2.52.5

1.251.25

NA NA

11

0.50.5

0.10.1

50050022

Pb-Pb runPb-Pb run pp runpp run

Event rate (Hz)Event rate (Hz)Event size (MB)Event size (MB)

Data in DAQ (GB/s)Data in DAQ (GB/s)

Data in EB (GB/s)Data in EB (GB/s)

Data on tape (GB/s)Data on tape (GB/s)

10 months10 months

11Run periodRun period

Total on tape (PB)Total on tape (PB)

Trigger typeTrigger type


The original The original architecturearchitecture


Detector Data LinkDetector Data Link

Functions:Functions:• main interface with the detectorsmain interface with the detectors• handle detector-to-LDC data flowhandle detector-to-LDC data flow• handle LDC-to-detector commands & handle LDC-to-detector commands & datadata

Functions:Functions:• main interface with the detectorsmain interface with the detectors• handle detector-to-LDC data flowhandle detector-to-LDC data flow• handle LDC-to-detector commands & handle LDC-to-detector commands & datadata

Keywords:Keywords:• cheapcheap• smallsmall• functionalfunctional• rad-hardrad-hard• long distancelong distance• opticaloptical• used used everywhereeverywhere

Keywords:Keywords:• cheapcheap• smallsmall• functionalfunctional• rad-hardrad-hard• long distancelong distance• opticaloptical• used used everywhereeverywhere


Local Data ConcentratorLocal Data ConcentratorFunctions:Functions:• handle and control the local DDL(s)handle and control the local DDL(s)• format the dataformat the data• perform local event buildingperform local event building• allow monitoring functionsallow monitoring functions• ship events to the event builders ship events to the event builders (GDCs)(GDCs)

Functions:Functions:• handle and control the local DDL(s)handle and control the local DDL(s)• format the dataformat the data• perform local event buildingperform local event building• allow monitoring functionsallow monitoring functions• ship events to the event builders ship events to the event builders (GDCs)(GDCs)

Keywords:Keywords:• distributeddistributed• good data moving good data moving capabilitiescapabilities

from the DDLfrom the DDL to the Event Building to the Event Building LinkLink

• CPU power not CPU power not indispensableindispensable• Not a farmNot a farm


from the DDLfrom the DDL to the Event Building to the Event Building LinkLink

• CPU power not CPU power not indispensableindispensable• Not a farmNot a farm


Global Data Global Data CollectorCollectorFunctions:Functions:

• accept the data sent from the LDCsaccept the data sent from the LDCs• perform final event buildingperform final event building• ship the events to the Permanent Data Storage ship the events to the Permanent Data Storage (PDS)(PDS)

Functions:Functions:• accept the data sent from the LDCsaccept the data sent from the LDCs• perform final event buildingperform final event building• ship the events to the Permanent Data Storage ship the events to the Permanent Data Storage (PDS)(PDS) Keywords:Keywords:

• distributeddistributed• good data moving good data moving capabilitiescapabilities

from the LDCsfrom the LDCs to the PDSto the PDS

• CPU power not CPU power not indispensableindispensable• farmfarm


from the LDCsfrom the LDCs to the PDSto the PDS

• CPU power not CPU power not indispensableindispensable• farmfarm


Event Destination Event Destination ManagerManager

Functions:Functions:• collect availability information from the GDCscollect availability information from the GDCs• distribute event distribution policies to the data distribute event distribution policies to the data sourcessources

Functions:Functions:• collect availability information from the GDCscollect availability information from the GDCs• distribute event distribution policies to the data distribute event distribution policies to the data sourcessources

Keywords:Keywords:• optimized network optimized network usageusage• look ahead capabilitieslook ahead capabilities

Keywords:Keywords:• optimized network optimized network usageusage• look ahead capabilitieslook ahead capabilities


Event Building LinkEvent Building Link

Keywords:Keywords:• big events (1-3, 67-87 MB)big events (1-3, 67-87 MB)• low rates (20, 500, 670 Hz)low rates (20, 500, 670 Hz)• many-to-manymany-to-many• mainly unidirectionalmainly unidirectional

Keywords:Keywords:• big events (1-3, 67-87 MB)big events (1-3, 67-87 MB)• low rates (20, 500, 670 Hz)low rates (20, 500, 670 Hz)• many-to-manymany-to-many• mainly unidirectionalmainly unidirectional

Functions:Functions:• Move data from the LDCs to the Move data from the LDCs to the GDCsGDCs

Functions:Functions:• Move data from the LDCs to the Move data from the LDCs to the GDCsGDCs


Overall key conceptsOverall key concepts Keep forward flow of dataKeep forward flow of data Allow back-pressure at all levels (DDL, EBL, STL)Allow back-pressure at all levels (DDL, EBL, STL) Standard Hw and Sw solutions sought:Standard Hw and Sw solutions sought:

ALICE collaborationALICE collaboration CERN computing infrastructureCERN computing infrastructure

Whenever possible go COTSWhenever possible go COTS During the pp run, keep any unused hardware busyDuring the pp run, keep any unused hardware busy


Mismatch of ratesMismatch of rates Recent introduction of:Recent introduction of:

Transition Radiation Detector (TRD)Transition Radiation Detector (TRD) Dielectron triggerDielectron trigger change in Pixel event sizechange in Pixel event size increase in estimated TPC average occupancyincrease in estimated TPC average occupancy

Required throughput an order of magnitude too high!Required throughput an order of magnitude too high! New scenarios:New scenarios:

region-of-interest readoutregion-of-interest readout online compressiononline compression online reconstructiononline reconstruction introduction of a level 3 triggerintroduction of a level 3 trigger


The new The new architecturearchitecture

FEE: Front-End ElectronicDDL: Detector Data LinkRORC: Read-Out Receiver CardFEDC: Front-End Digital Crate/ComputerEBL: Event Building LinkLDC: Local Data ConcentratorGDC: Global Data CollectorEDM: Event Destination ManagerTDL: Trigger Distribution LinkFCL: Flow Control LinkPDS: Permanent Data StorageSTL: Storage Link

Nov-99

PDS

Switch EDM

Time Projection Chamber

InnerTrackingSystem

PhotonSpectrometer

2.5-5 GBytes/sec. Pb-Pb run500 MBytes/sec. p-p run

20Hz central + 20Min. Bias +1000 Hz dimuon + 200Hz diel. Pb-Pb500 Hz p-p5.5 - 100 us

FEDC

FEE

ParticleIdentification

4000 Hz Pb-Pb1200 Hz p-p1.2 us 2.7 us

1250 MBytes/sec. Pb-Pb run100 MBytes/sec. pp run

DDL

EBL

1100 Hz Pb-Pb1000 Hz p-p5.5 us

Switch

STL

TriggerData

Trigger DecisionsDetector busy

FEEFEEFEEFEE

PDS PDS PDS

Trigger Detectors: - Micro Channel Plate- Zero-Degree Calorimeters- Muon Trigger Chambers- Transition Radiation Detector

MuonTrackingChambers

FEDC FEDC FEDC FEDC

FCL

L0 Trigger

FEE

Interaction rate

8 103 Hz Pb-Pb

105 Hz p-p

RORCRORCRORC

LDCLDCLDCLDCLDC

L3 GlobalTrigger

FEDC

RORCRORCRORC

RORCRORCRORC

RORCRORCRORC

FEEFEE

RORC RORC L1 Trigger

L2 Trigger

GDC

L3

L3

L3

L3

GDC

L3

L3

L3

L3

GDC

L3

L3

L3

L3

GDC

L3

L3

L3

L3

L3 Filter& Partial

L3 Filter& Partial

LDC


The Event Building The Event Building processprocess

Events flow asynchronously into the LDCsEvents flow asynchronously into the LDCs Each LDC performs - if needed - local event buildingEach LDC performs - if needed - local event building The Level 3 farm - if present - is notifiedThe Level 3 farm - if present - is notified Level 3 decision - if any - is sent to LDCs and GDCLevel 3 decision - if any - is sent to LDCs and GDC All data sources decide where to send the data according to:All data sources decide where to send the data according to:

directives from the Event Destination Manager directives from the Event Destination Manager the content of the eventthe content of the event

The chosen GDC receives:The chosen GDC receives: sub-eventssub-events optional reconstructed and compressed dataoptional reconstructed and compressed data optional level 3 decisionoptional level 3 decision

The Event Building Link does the restThe Event Building Link does the rest


Software Software environmentenvironment

DATEDATE Data acquisition environment for ALICE and test beamsData acquisition environment for ALICE and test beams Support DDLs, LDCs, GDCs and liaison to the PDSSupport DDLs, LDCs, GDCs and liaison to the PDS Standalone and complex DAQ systemsStandalone and complex DAQ systems Integrated with HPSS and CASTOR (via CDR)Integrated with HPSS and CASTOR (via CDR) Keywords:Keywords:

CC TCP/IPTCP/IP Tcl/TkTcl/Tk JavaJava ROOTROOT


Data challengesData challenges Use state-of-the-art equipment for real-life exerciseUse state-of-the-art equipment for real-life exercise 1998-1999: Challenge I1998-1999: Challenge I

7 days @ 14 MB/s, 7 TB7 days @ 14 MB/s, 7 TB 1999-2000: Challenge II1999-2000: Challenge II

2 * 7 days @ max 100 MB/s, > 20 TB2 * 7 days @ max 100 MB/s, > 20 TB transfer simulated TPC datatransfer simulated TPC data 23 LDCs * 20 GDCs (AIX/Solaris/Linux)23 LDCs * 20 GDCs (AIX/Solaris/Linux) with offline filtering algorithms and online objectifier with offline filtering algorithms and online objectifier

(ROOT)(ROOT) two different MSS (HPSS and CASTOR)two different MSS (HPSS and CASTOR) several problems several problems limited stability limited stability


Data Challenge IIData Challenge II






0.0

20.0

40.0

60.0

80.0

100.0

120.0

140.0

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Number of event builders

Glo

bal t

hrou

ghpu

t (M

B/s)

Event building Event building networknetwork

Pure Linux setup20 data sourcesFastEthernet local connectionGigaBit Ethernet backbone


Run logRun log


Data Challenge IIIData Challenge III Will run during the winter 2000-2001 shutdownWill run during the winter 2000-2001 shutdown Target: 100 MB/s (or more) Target: 100 MB/s (or more) sustainedsustained over [7..10] days over [7..10] days Improved stabilityImproved stability More “ALICE like” setupMore “ALICE like” setup

abandon older architectures still in use at the test beamsabandon older architectures still in use at the test beams Implement 10% of the planned ALICE EB throughputImplement 10% of the planned ALICE EB throughput Integrate new modules & prototypes:Integrate new modules & prototypes:

improved event buildingimproved event building Level 3Level 3 Regional CentersRegional Centers

Will use the LHC computing testbedWill use the LHC computing testbed Better status reporting tools: use PEM if availableBetter status reporting tools: use PEM if available

Date post:	10-Jan-2016
Category:	Documents
Upload:	dasan
View:	28 times
Download:	3 times

LHC experiments Requirements and Concepts ALICE

Documents