1. ALICE Data Challenges
Fons Rademakers
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2. Data Challenge
When fully operational ALICE will take data with a rate of 1.5 GB/s
An order of magnitude higher than any of the other LHC experiments
Since we are unique we can not piggyback on ATLAS/CMS/IT R&D

3. Objectives
Simulate the ALICE on-line and off-line data recording and processing chain
Track technologies:
DATE, ROOT, MSS, networking, CPU's and OS'es
Repeat frequently to collect data points to see if we will be ready for 1.5 GB/s in 2005
Be ready for T=0 with as little surprises as possible

4. First Data Challenge
To store 10TB of raw data in a ROOT DB on HPSS within 5 days (i.e. 25 MB/s)
To test the following technologies:
DATE, ROOT, HPSS, GB ethernet, Linux and PC's
Very simple event model, but fairly realistic raw, tag and catalogue database environment
Executed in March 1999

5. ADC1 Data Flow 5 node cluster NA57 Data source Computer center
PowerPC/AIX
Intel/Linux PC
ROOT
objectifier
LDC
pipe
5 MB/s
GDC
Event Builder
switch
GB eth
LDC
rfcp
5 MB/s
disk
GB eth
DATE = LDC+GDC
5 MB/s
HPSS
RS6000/AIX
5 node cluster

6. DATE Data Source
DATE is developed by the ALICE DAQ team and used by NA57 and COMPASS
See talk by R. Divia (B293) this afternoon
LDC = Local Data Concentrator
GDC = Global Data Collector
In this setup the LDC's generated bit patterns simulating (NA57) events (size KBytes/event)

8. RAW Data DB Raw data DB contains AliEvent objects, which contain:
an AliEventHeader object
16 data members (72 bytes)
an AliRawData object
char array (variable length, kB)
AliEvent objects are stored in a single TTree container with two branches (for the two contained objects)

9. RAW Data DB (cont.) No compression (need more CPU power)
Size of individual raw DB's typically between 250 MB and 1.5 GB (tunable parameter)
As soon as a raw DB is closed it is moved to HPSS via rfcp (part of CERN SHIFT software interfaced to HPSS)

10. Tag DB Tag DB contains AliEventHeader objects, which contain:
size, type, run number, event number, burst number, trigger, time, detector id, etc.
AliEventHeader objects are stored in a single TTree with 16 branches (one for each header data member)
Compressed
Stays on disk
Used for fast event selection

11. Run Catalog DB
Run DB contains one AliStats object per produced raw data DB
An AliStats object contains:
filename of raw DB, number of events, begin/end run number, begin/end event number, begin/end time, file size of raw DB, compression factor, quality histogram (TH1F)
Compressed
Stays on disk
Used for matching run/event with raw DB

12. This was one of the largest OODB's in HEP !

15. Intel/Linux PC Cluster
NA57 Data source
Computer center
9 PowerPC/AIX
LDC
5 MB/s
Intel/Linux PC Cluster
LDC
Switch
Event
Filter
5 MB/s
GDC
Event Builder
GB eth
ROOT
objectifier
Switch
Pipe
5 IntelPC/Linux
LDC
10 MB/s
Switch
10 MB/s
GB eth
LDC
10 MB/s
Catalog
Tag DB
HPSS/
CASTOR
MSS
Alice DAQ Lab Data source
DATE = LDC+GDC
20 node cluster