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General: 

General We commend US ATLAS S&C for progress made during the past year, for the careful evaluation of the experiment’s computing requirements and the thorough Computing TDR, and for the very clear presentations during the review. US ATLAS S&C should continue to carefully examine whether the specific computing model choices cannot be further optimized. US ATLAS has been responsive to the suggestions of previous year’s review: e. g. change control has been implemented and appears to be working, Implementation of an analysis support model,

General 2: 

General 2 The distributed Tier 2 model leverages multiple university infrastructures effectively Ref. Rome WS grid production The planning for the transition from construction to operations appears appropriate: Careful planning of the Computing System Commissioning (CSC)

RAC: 

RAC A resource allocation committee (RAC) has been set up. We commend US ATLAS S&C for anticipating this important need The efficacy of this body may be limited by its size and composition The membership should be revisited as experience accrues

Collaboration Growth: 

Collaboration Growth We note that the number of US collaborators in ATLAS is likely to increase A rational mechanism to control the growth was presented, Computing costs for additional collaborators were estimated: Increased computing needs both at Tier 1 and Tier 2 to support additional US scientists. The committee finds this defensible. More US collaborators require additional Tier 1 and Tier 2 resources to support analysis We believe that the collaboration should remain open in spite of pressure on resources They should continue to assess the physics priorities and computing needs, Pursue other funding opportunities, Work with the funding agencies to obtain adequate resources.

Analysis Support: 

Analysis Support DC2 and the Rome workshop have revealed the current lack of user support (as noted during this review 2 years ago…) A user support model based on three Analysis Support Centers (ASC) and an Analysis Support Group (ASG) has been agreed upon. This model requires significant funding (~1M$/y) which is currently not identified We recommend that US ATLAS optimize their planning such as to accommodate the analysis support within their projected budget

Funding in 2008 and beyond: 

Funding in 2008 and beyond There is a funding contention of the order of 3M$/y in 2008 and beyond between M&O, Computing and Upgrade R&D. This is a concern since the planning already appears subcritical. However this is an internal ATLAS issue and it should be resolved accordingly.

Dependence on Grid Technologies: 

Dependence on Grid Technologies The 2005 DC2 and Rome WS have exposed risks due to poorly performing grid deliverables. PanDA is a reasonable way of dealing with these dependencies. We endorse the plan of integrating additional GRID deliverables as they become available and robust

US ATLAS: Facilities & Grids: 

US ATLAS: Facilities & Grids

Tier1 - Observations: 

Tier1 - Observations Note that BNL has started charging explicitly for power for the Tier1 facility. The projected power consumption may be a factor of 2 too low and US ATLAS is following up on this and there is additional uncertainty on projected cost. Projected manpower profile (ramp up) is a reasonable plan. A manpower reduction caused by not receiving the anticipated $2M MR in FY08 and beyond would cause serious risk in the ability of the Tier1 facility to provide the required functionality. US ATLAS has chosen to deploy disk-based event store using dCache managed disk distributed on compute nodes. This allows reduced hardware cost compared to traditional disk arrays but may cause an increase of risk due to use at unprecedented scale.

Tier2 - Observations: 

Tier2 - Observations Three Tier2 centers have been awarded and established. Each of these is a multi-site installation. Some have achieved significant leveraging of resources. There has been some work on addressing the physics analysis & user support questions and relation between a Tier2 and an Analysis Support Center.

Network - Observations: 

Network - Observations Tier1 WAN connection is not redundant. This is understood as an issue that is being investigated but at present there is not a concrete plan to add it. The Tier2 connectivity planned is more than adequate and is expected to achieve 10 Gbps at each site by end of 2007.

Grids - Observations: 

Grids - Observations The OSG “volunteer effort” is currently providing the VDT software, software validation, integration, and operations which US ATLAS depends upon. Many of these functions would need to be picked up by US ATLAS if OSG is not funded. We note that the PanDA controlled job submission failure rate is significantly reduced compared to the system it replaced and it has provided the ability to handle significantly higher rate of job submission.

Recommendations: 

Recommendations We recommend further efforts to understand the effect and usage model of individual physicists at the Tier2 centers and relation to the Analysis Support Centers. US ATLAS should apply all available pressure to the grid middleware projects to get middleware personnel engaged in the service challenges this year and scaling problems addressed. We recommend that US ATLAS pursue acquisition of redundant network connectivity to the Tier1 center. We recommend to test the scalability of the dCache managed distributed disk.

ATLAS Core Software: 

ATLAS Core Software Core software has matured considerably since last presented. Necessary support of the DataChallenges and Physics meetings happened. PanDA appears to be a targeted solution to the failures seen in the Data Challenges, and will provide better automation and database handling of datasets While the datasets facilitate the finding of data, it may be of quite coarse granularity and cause more than intended data movement traffic For example, a Tier 3 site with 2TB of disk might have difficulties swallowing a dataset The Core Framework group has delivered a working product and is now in a mode of maintenance, small upgrades and (if they can) longer term upgrades. They are collecting input from the community on usability. The Data Management group is concentrating on the details of efficient use of Root with ATLAS data, including looking at the details of tag databases and schema evolution, as well as I/O efficiency.

Recommendations: 

Recommendations Devise a plan to test how well the schema evolution solution works Revisit the analysis support group staffing periodically to determine whether it is working effectively, especially viz a viz the use of software professionals in this role. Examine use case tradeoffs between advantages of centrally defined datasets vs downside of potential traffic increase Ensure definition of finer-grained datasets is supported