Transcript The story of BaBar: an IT perspective Roger Barlow DESY 4

The story of BaBar: an IT
perspective
Roger Barlow
DESY 4th September 2002
Example:  -  0
OPAL
Roger Barlow 4 Sept 2002
BaBar
(Work in progress)
BaBar: an IT perspective
Slide 2/18
History
1995
TDR
1999
First data
2000
First results
0.5 fb-1 Objectivity /
kanga
23 fb-1 File transfer
2001
Sin 2b= 0.590.140.05
39 fb-1 Tier A sites
2002
Sin 2b= 0.7410.0670.029
28 fb-1 Grid
Roger Barlow 4 Sept 2002
C++
BaBar: an IT perspective
Slide 3/18
Datataking:
“Drinking from a firehose”
4.2 ns
32 SUN U5
L1 Trigger
L3 Trigger
1-2kHz
200+ CPUs
PowerPCs in
VME crates
OPR farm
30-100 Hz
Data store
200 kB/evt
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 4/18
C++
Decision taken:
approved languages
C++ and F90
(Nobody used F90)
HEP escapes at last
from FORTRAN!
Other experiments
follow
Software immediately
becomes VERY
object-oriented
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
“Unorthodox
but very nice
introduction to
programming”
Amazon.com
review
Slide 5/18
C++ in practice
Old
Design
New
Abstract objects
EmcCluster:AbsRecoCalo
AbsRecoCalo: AbsEvtObj
EmcClusterMoments:
EmcAbsClusterProperty
EmcClusterDistance:
EmcAbsClusterProperty
The software was written on time and it worked.
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 6/18
Some lessons
RogueWave
Commercial class library
Built in to software from
start
Superseded by STL,
CLHEP
Licence arrangements
restrictive/expensive
Now (painfully) removed
Roger Barlow 4 Sept 2002
Calibration
System impressive technically
Can’t do what you want it to
Event Display
Powerful system (‘Event display
server’) written by experts
Unwieldy and unreliable for nonexperts away from SLAC
Little used
BaBar: an IT perspective
Slide 7/18
Objectivity
•
•
•
•
•
‘Persistent data’
Objects still present
when a job is run againstored on disc
Need to handle pointers
Need to match data on
disk to objects the
program knows about
Need to do this fast and
furiously
Objectivity does this –
no alternative
Roger Barlow 4 Sept 2002
• Performance issues in
OPR: solved (hard
work+vendor cooperation)
• Performance issues in
analysis: not
satisfactory (physicists
more random) KANGA
• Long-term viability?
BaBar: an IT perspective
Slide 8/18
Success: the
penalty
PEPII delivers
and BaBar can handle it
Design Luminosity 3 1033
achieved
Now 5 1033
Heading for 4 1034
BaBar efficiency ~ 95%
Data handling
Need to provide
• Disk (or tape) for data
storage
• Machines for OPR
• Machines for analysis
Moore’s Law is not strong
enough
(This is a race. KEK and
Belle are close behind!)
Need new computing model
Central  Distributed
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 9/18
File Transfer
Data transfer
From SLAC to outside sites
Large (RAL, IN2P3) and
small (university)
Use network transfer
rather than shipping
tapes
ESNET in US, JANET+
GEANT in Europe
Use RAL, Rome, etc as
staging posts
Roger Barlow 4 Sept 2002
File copy programs
bbcp and bbftp developed,
now standard
Copy with multiple
streams
Achieve 80-100 Mbit/s
Data available within days
Chasing improvement
continuous task
BaBar: an IT perspective
Slide 10/18
Spreading the load
Serious computing power at
outside institutes
Each UK BaBar group
~1TB fast disc (1998)
Compute farm (80 CPU)
(2000)
Used for analysis
Used for MC simulation
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 11/18
RAL Tier A Centre
UK GRID Funds available
Tier 1/A centre at RAL
200+ CPUs 35 TB disk this
year (increasing as price
drops)
Rebate on common fund
contribution
Everybody happy
Roger Barlow 4 Sept 2002
Similar centres at IN2P3, Bologna,
plus Karlsruhe in future
BaBar: an IT perspective
Slide 12/18
Future Development
Many users running jobs
on distributed data
with distributed CPUs
Don’t want technical detail
MC:RB
Roger Barlow 4 Sept 2002
GRID provides the answer
User specifies data description
and job
Grid tools locate files, find
CPUs, submit jobs
BaBar today: LHC tomorrow
BaBar: an IT perspective
Slide 13/18
Authentication
Grid
Certificate
Uses RSA encryption to
prove to other
computers
(‘gatekeepers’) that you
are who you say you are
Roger Barlow 4 Sept 2002
Certificate Authorities
Certificates issued by
trusted organisations to
people they know and
trust
(or people they trust know
and trust)
Establish mutual trust
within BaBar for
UKHEP,CNRS, etc
But authentication is not
authorisation!
BaBar: an IT perspective
Slide 14/18
Authorisation
SLAC
MANCHESTER
BaBarGrid
sites
gridmap files
Grid
Certifica
te
cron
job
BaBar
VO list
cron
job
Users with Grid certificates authorised to use resources at all BaBarGrid sites
Getting on this list is made easy (for BaBar users with a Grid certificate)
Dynamic account pool avoids need for 500x50 userids
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 15/18
The BaBar VO
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 16/18
The BaBar Grid
Demonstrator
Rudimentary Grid
submission
and retrieval
Full features to be
added later
Roger Barlow 4 Sept 2002
BaBar: an IT perspective
Slide 17/18
The Future: Some
Possibilities
Join EDG
testbed rollout
More Compute and
Storage farms
Desk-to-desk
Video
conferencing
SRB as universal
file system
Framework VI
Roger Barlow 4 Sept 2002
Extend VO
system for
authorisation
Metadata specification
using xml
BaBar: an IT perspective
Slide 18/18