1. CMS-HI Offline Computing
Charles F. Maguire Vanderbilt University
For the CMS-HI US Institutions
May 14, 2008
Draft Version 4 on May 13 at 2:30 PM CDT

2. CMS-HI at the LHC for High Density QCD with Heavy Ions
LHC: New Energy Frontier for Relativistic Heavy Ion Physics
Quantum Chromodynamics at extreme conditions (density, temperature, …)
Pb+Pb collisions at 5.5 TeV, thirty times larger than Au+Au at RHIC
Expecting a longer-lived Quark Gluon Plasma state accompanied by much enhanced yields of hard probes with high mass and/or transverse momentum
CMS: Excels as a Heavy Ion Collisions Detector at the LHC
Sophisticated high level trigger for getting rare important events at a rapid rate
Best momentum resolution and tracking granularity
Large acceptance tracking and calorimetry --> proven jet finding in HI events
May 14, 2008
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3. Draft Version 4 on May 13 at 2:30 PM CDT
CMS-HI in the US
10 Participating Institutions
Colorado, Iowa, Kansas, LANL, Maryland, Minnesota, MIT, UC Davis, UIC, Vanderbilt
Projected to contribute ~60 FTEs (Ph.D. and students) as of 2012
MIT as lead US institution with Boleslaw Wyslouch as Project Manager
US-CMS-HI Tasks (Research Management Plan in 2007)
Completion of HLT CPU Farm Upgrade for HI events at CMS (MIT)
Construction of the Zero Degree Calorimeter at CMS (Kansas and Iowa)
Development of the CMS-HI Compute Center in the US (task force established)
Task force recommended that the Vanderbilt University group lead the proposal composition
Also want to retain the expertise developed by the MIT HI group at their CMS Tier2 site
CMS-HI Compute Proposal to DOE is Due This Month
Will be reviewed by ESnet managers, and also by external consultants
May 14, 2008
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4. Basis of Compute Model for CMS-HI
Heavy Ion Data Operations for CMS at the LHC
Heavy ion collisions expected in 2009, second year of running for the LHC
Heavy ion running takes place during a 1 month period (106 seconds)
At designed DAQ bandwidth the CMS detector will be writing 225 TBytes of raw data per heavy ion running period, plus ~75 TBytes support files
Raw data will likely stay resident at CERN Tier0 disks for a few days at most, while transfers take place to the CMS-HI compute center in the US
Possibility to have 300 TBytes of disk dedicated to HI data (NSF REDDnet project)
Raw data will not be reconstructed at the Tier0, but will be written to a write-only (emergency archive) tape system before deletion from Tier0 disks
Projected Data Volumes (optimistic scenario)
Assumes that we don’t need 400 TBytes of disk space immediately
TBytes in first year of HI operations
TBytes in second year of HI operations
300 TBytes nominal size achieved in third year of HI operations
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Data Transport Options for CMS-HI Following ESnet-NP 2008 Workshop Recommendations
CMS-HEP Raw Data Transport from CERN to FNAL Tier1
Using LHCnet to cross the Atlantic
LHCnet terminating at Starlight HUP
ESnet transport from Starlight into FNAL Tier1 centre
Links are rated at 10 Gbps
CMS-HI Raw Data Transport from CERN to US Compute Center
Network topology has not been established at this time
Vanderbilt is establishing a 10 Gbps path to SOX-Atlanta for end of 2008
Network Options (DOE requires a non-LHCnet backup plan)
Use LHCnet to Starlight during one month when HI beams are being collided Transport data from Starlight to Vanderbilt compute center via ESnet/Internet2 Transfer links will still be rated at 10 Gbps to transfer data within ~1 month
Do not use LHCnet but use other trans-Atlantic links supported by NSF, with links rated at 10 Gbps such that data are transferred over ~1 month
Install 300 TByte disk buffer at CERN and use non-LHCnet trans-Atlantic links to transfer data over 4 months (US-Alice model) at ~2.5 Gbps
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6. Vanderbilt to SoX Using Managed Service Connecting 10G to ACCRE only
May 14, 2008
Vanderbilt I n f o r m a t i o n T e c h n o l o g y S e r v i c e s
Vanderbilt I n f o r m a t i o n T e c h n o l o g y S e r v i c e s 6

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Data Transport Issues for CMS-HI Following ESnet-NP 2008 Workshop Recommendations
To Use LHCnet or Not To Use LHCnet
Use of LHCnet to US, following CMS-HEP path, is the simplest approach
A separate trans-Atlantic link will require dedicated CMS-HI certifications
DOE requires a non-LHCnet plan be discussed in CMS-HI compute proposal
Issues With the Use of LHCnet by CMS-HI
ESnet officials believe that LHCnet is already fully subscribed by FNAL
HI month was supposed to be used for getting final sets HEP data transferred
FNAL was quoted as having only 5% “headroom” left with use of LHCnet
HI data volume is 10% of the HEP data volume
Issues With the Non-Use of LHCnet by CMS-HI
Non-use of LHCnet would be a new, unverified path for data out of the LHC
CERN computer management would have to approve (same for US-ALICE)
Installing a 300 TByte disk buffer system at CERN (ESnet recommendation) would also have to approved and integrated into the CERN Tier0 operations
May 14, 2008
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8. Tape Archive for CMS-HI? Raw Data and Processed Data for Each Year
CMS-HI Raw Data Tape Archive: FNAL or Vanderbilt?
Original suggestion was that the raw data archive be at Vanderbilt Vanderbilt already has a tape robot system, can upgrade to 1.5 more PBytes
Possibly more economical to archive the raw (and processed) data at FNAL? Savings are a result of not having a person at VU dedicated to tape service
Cost savings result in more CPUs for the CMS-HI compute center
Issues for Tape Archive Decision
Is there a true cost savings ($135K over 5 years) as anticipated? [see slide 10]
What specific new burdens would be assumed at FNAL?
Serving raw data twice per year to Vanderbilt for reconstruction
Receiving processed data annually for archiving into tape system
Is the tape archive decision coupled with the use/non-use of LHCnet?
Administrative issue of transferring funds from DOE-NP to DOE-HEP
May 14, 2008
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9. Data Processing for CMS-HI
Real Data Processing Model
Two reconstruction passes per year taking 4 months each
Two following analysis passes per year taking 2 months each
Analyzed data placed at selected data depots (MIT, UIC, Vanderbilt)
A CMS-HI Tier2 center is also forecast to exist in South Korea
All CMS-HI institutions access AOD files via OSG job submissions
Real Data Output File Production Model
Normal reco output is 20% of raw data input
Reco output with diagnostics is 400% of raw data input (only for initial runs)
CPU Processing Requirement
Extensive (several months) studies with MC HI events done at MIT Tier2
MC studies done with current CMSSW framework
Conclusion that ~2900 CPU cores will be required for nominal year running
Cores at SpecInt2K 1600 equivalent (obsolete unit, will do actual bench testing)
Ramp up to nominal year will require fewer cores with fewer complex events
May 14, 2008
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10. NOTE: None of these scenarios includes costs for network transfers
Implementation of CMS-HI Compute Center Three Scenarios Being Considered
Raw Data + Output Production Archived on Tape at FNAL
Cost transfer of $35K/year to FNAL, obtains 2.23 PBytes of tape in 5 years
Five year sequence: TBytes of tape
Cost savings estimated at $135K over 5 years
After 5 years there will be 3000 CPU cores available at Vanderbilt
Raw Data + Output Production Archived on Tape at VU
Costs will include tapes and a dedicated FTE to support additional tape load
After 5 years there will be 2480 CPU cores available at Vanderbilt
Tape Archive at VU and 300 TBytes Buffer Disk at CERN
Buffer disk at CERN allows raw data to be transferred over 4 months instead of 1 month
Would need consultation with CERN Tier0 managers
Suggested by ESnet managers as a fallback if trans-Atlantic network is not fast enough
After 5 years there will be 2120 CPU cores available at Vanderbilt
Possible these 300 TBytes could be funded by a separate proposal, e.g. NSF REDDnet
NOTE: None of these scenarios includes costs for network transfers
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11. Draft Version 4 on May 13 at 2:30 PM CDT
Backup Slides 1) VU network topologies ( ) 2) Gunther’s spreadsheet (to be added)
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Add ORNL or Starlight later using Dark Fiber (unmanaged)
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LHCNet??
Fermilab??
*Would need to have peering or
layer 2 VLAN setup.
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