# Presentation: 224762

## U.S. ATLAS  Computing Facilities Overview

**Bruce G. Gibbard**
**Brookhaven National Laboratory**
- U.S. LHC Software and Computing Review
- Brookhaven National Laboratory
- November 14-17, 2000

## Facilities Presentations

- Overview – B. Gibbard
- Requirements
- Overall plan & rationale
- Network considerations
- Risk & contingency
- Details of Tier 1 – R. Baker
- Tier 1 configuration
- Schedule
- Cost analysis
- Grid Software and Tier 2’s – R. Gardner (Yesterday)
- Grid plans
- Tier 2 configuration
- Schedule & cost analysis

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## US ATLAS Computing Facilities

- ...to enable effective participation by US physicists in the ATLAS physics program!
- Direct access to and analysis of physics data sets
- Simulation, re-reconstruction, and reorganization of data as required to complete such analyses

- Facilities procured, installed and operated
- ...to meet U.S. “MOU” obligations to ATLAS
- Direct IT support (Monte Carlo generation, for example)
- Support for detector construction, testing, and calibration
- Support for software development and testing

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Setting the Scale

- For US ATLAS
- Start from ATLAS Estimate of Requirements & Model for Contributions
- Adjust for US ATLAS perspective (*experience, priorities and facilities model*)
- US ATLAS facilities must be adequate to meet all reasonable U.S. ATLAS computing needs
***Specifically, the U.S. role in ATLAS should not be constrained by a computing shortfall; it should be enhanced by computing strength***

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## ATLAS Estimate (1)

- New Estimate Made As Part of Hoffmann LHC Computing Review
- Current draft “ATLAS Computing Resources Requirements”, V1.5 by Alois Putzer
- Assumptions for LHC / ATLAS detector performance

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## ATLAS Estimate (2)

- Assumptions for ATLAS data

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Architecture

*Remote Tier 2 Computing Centers*
*Institutional Computing Facilities*
*Individual Desk Top Systems*

- Hierarchy of Grid Connected Distributed Computing Resources
***Primary Atlas Computing Centre at CERN***
*Tier 0 & Tier 1*
***Remote Tier 1 Computing Centers***

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Functional definitions

- Tier 0 Center at CERN
- Storage of primary raw and ESD data
- Reconstruction of raw data
- Re-procession of raw data
- Tier 1 Centers (At CERN & in some major contributing countries)
- Simulation and reconstruction of simulated data
- Selection and redefinition of AOD based on complete locally stored ESD set
- Group and User level analysis
- Tier 2 Centers
- Not described in the current ATLAS document, function as a reduced scale Tier 1’s, bringing analysis capability effectively closer to individual users

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Required Tier 1 Capacities (1)

- Individual ATLAS Tier 1 Capacities in 2006

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Required Tier 1 Capacities (2)

- Expect 6 Such Remote Tier 1 Centers
- USA, FR, UK, IT, +2 to be determined
- ATLAS Capacity Ramp-up Profile

**Perhaps too much too early, at least for US ATLAS facilities             ... see Rich Baker’s talks**

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## US ATLAS Facilities

- Requirements Related Considerations
*Analysis* is the dominant Tier 1 activity
- Experience shows *analysis* will be compute capacity limited
- Scale of US involvement is larger than other Tier 1 countries ... ***by authors, by institutions, by core detector fraction (x 1.7, x 3.1, x 1.8)***  so US will require more analysis than a single canonical Tier 1
- US Tier 1 must be augmented by additional capacity  (**particularly for *****analysis***)
- Appropriate US facilities level is ~ twice that of a canonical Tier 1

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## US ATLAS Facilities Plan

- US ATLAS will have a Tier 1 Center, as defined by ATLAS, at Brookhaven
- The Tier 1 will be augment by 5 Tier 2 Centers whose aggregate capacity is comparable to that of a canonical Tier 1
- This model will ...
- exploit high performance US regional networks
- leverage existing resource at sites selected as Tier 2’s
- establish an architect which supports the inclusion of institutional resources at other (non-Tier 2) sites
- focus on *analysis*: both increasing capacity and encouraging local autonomy and therefore presumably creativity within the analysis effort

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Tier 1 (WBS 2.3.1)

- Tier 1 is now operational with significant capacities at BNL
- Operating in coordinating with the RHIC Computing Facility (RCF)
- Broad commonality in requirements between ATLAS and RHIC
- Long term synergy with RCF is expected
- Personnel & cost projections for US ATLAS facilities are base on recent experience at RCF ... *see Rich Baker’s talk*
- Technical choices, beyond simple price/performance criteria, must address issues of maintainability, manageability and evolutionary flexibility
- Current default technology choices used for costing will be adjusted to exploit future technical evolution (toward more cost effective new options)

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

##  Tier 1 (continued)

- Full Tier 1 Functionality Includes ...
- Hub of US ATLAS Computing GRID
- Dedicated High Bandwidth Connectivity to CERN, US Tier 2’s, etc.
- Data Storage/Serving
- Primary site for caching/replicating data from CERN & other data needed by US ATLAS
- Computation
- Primary Site for any US Re-reconstruction (perhaps only site)
- Major Site for Simulation & Analysis
- Regional support plus catchall for those without a region
- Repository of Technical Expertise and Support
- Hardware, OS’s, utilities, other standard elements of U.S. ATLAS
- Network, AFS, GRID, & other infrastructure elements of WAN model

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## GRID R&D (WBS 2.3.2.1 - 2.3.2.6 )

- Transparent, Optimized Use of Wide Area Distributed Resources by Means of “*Middleware****”***
- Significant Dependence on External (***to both US ATLAS and ATLAS***) Projects for GRID Middleware
- PPDG, GriPhyN, European DataGrid
- Direct US ATLAS Role
- Specify, Adapt, Interface, Deploy, Test and Use
*...   **Rob Gardner’s talks **(yesterday)*

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Tier 2 (WBS 2.3.2.7 - 2.3.2.11 )

- The *standard* Tier 2 configuration will focus on the CPU and cache disk required for *analysis*
- Some Tier 2’s will be custom configured to leverage particularly strong institutional resources of value to ATLAS (the current assumption is that there will be 2 HSM capable sites)
- Initial Tier 2 selections (2 sites) will be base on their ability to contribute rapidly and effectively to development and test of this Grid computing architecture

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Network

- Tier 1 Connectivity to CERN and to Tier 2’s is Critical to Facilities Model
- Must have adequate bandwidth
- Must eventually be guaranteed and allocable bandwidth (dedicated and differentiate)
- Should grow with need; OC12 to CERN in 2005 with OC48 needed in 2006
- While the network is an integral part of the US ATLAS plan, its funding is not part of the US ATLAS budget

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## WAN Bandwidth Requirements

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Capacities of US ATLAS Facilities

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Risks and Contingency

- Have Develop Somewhat Conservative but Realistic Plans and Now Expect to Build Facilities to Cost
- Contingency takes the form of reduction in scale (***design is highly scaleable***)
- Option to trade one type of capacity for another is retained until very late (**~*****80% of procured capacity occurs in ’06***)

- Risk Factors
- Requirements may change
- Price/performance projections may be too optimistic
- Tier 2 funding remains less than certain
- Grid projects are complex and maybe be less successful than hoped

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000

## Summary

- The US ATLAS Facilities Project Has Three Components
- Tier 1 Center at BNL ... ***as will be detailed in Rich Baker’s talk***
- 5 Distributed Tier 2 Centers ...
- Network & Grid tying them together ...
- Project’s Integral Capacity Meets the ATLAS/LHC Computing Contribution Guidelines and Permits Effective Participation by US Physicists in the ATLAS Research Program
- Approach Will Make Optimal Use Of Resources Available to US ATLAS and (*in a Funding Limited Context*) Will Be Relatively Robust Against Likely Project Risks

- } ***as was discussed in Rob Gardner’ talk***

- B. Gibbard                  US ATLAS Computing Facilities Overview

- 16 November, 2000