# Presentation: 224763

## U.S. ATLAS  Computing Facilities Overview

**US ATLAS Computing Advisory Panel Meeting**
**October 25-27, 2000**
**Bruce G. Gibbard, BNL**

## Facilities Presentations

**Overview – B. Gibbard**
**Computing requirements**
**Network considerations**
**Overall plan & rationale**
**Details of Tier 1 – R. Baker**
**Tier 1 configuration**
**Cost & schedule analysis**
**Details of Tier 2’s and Grid – R. Gardner**
**Tier 2 configuration**
**Grid plan**
**Cost & schedule analysis**

- B. Gibbard

- 26 October, 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 analysis**

**Facilities procured, installed and operated**
**...****to meet U.S. ‘*****MOU’ *****obligations to ATLAS**
**Direct IT capacity (Monte Carlo, for example)**
**Support for detector construction, testing, & calib.**
**Support for software development and testing**

- B. Gibbard

- 26 October, 2000

## Setting the Scale

**Significant Uncertainty in Defining Scale of ATLAS Computing Needs**
***Accelerator and detector far from completed***
***Five years of algorithm & software development***
***Five years of computer technology evolution***
**For US ATLAS**
**Start from ATLAS Estimate of Requirements & Model for Contributions **
**Adjust for US ATLAS perspective (*****experience, priorities and facilities model*****)**

- B. Gibbard

- 26 October, 2000

## US ATLAS Perspective

**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*****)**
**There needs to be significant capacity beyond that formally committed to International ATLAS which can be allocated at the discretion  of U.S. ATLAS among its analysis efforts**

- B. Gibbard

- 26 October, 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

- 26 October, 2000

## ATLAS Estimate (2)

**Assumptions for ATLAS data**

- B. Gibbard

- 26 October, 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

- 26 October, 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 countries)**
**Simulation and reconstruction of simulated data**
**Selection and redefinition of AOD**
**User Analysis**
**Tier 2 Centers**
**Less clearly defined, reduced scale (& functionality?) Tier 1**

- B. Gibbard

- 26 October, 2000

## Required Tier 1 Capacities

**Individual Tier 1 Center Capacities in 2006**
**CPU: 209 kSPi95**
**Disk: 365 TBytes**
**Tape: 1800 Tbytes**
**Expect 6 Such Remote Centers**
**USA, FR, UK, IT, +2 to be determined**
**Capacity Ramp-up Profile**
**(Perhaps too much too early, as Rich Baker will discuss)**

- B. Gibbard

- 26 October, 2000

## US ATLAS Facilities

**Requirements Related Considerations**
***Analysis***** is the dominant Tier 1 activity**
**Experience shows *****analysis***** will be compute capacity limited**
**US scale is larger than other Tier 1 countries ...                   **** by authors, by institutions, by core fraction**** ****(x 1.7, x 3.1, x 1.8)   ****and so will require more analysis than a single canonical Tier 1**
**US effort within itself is more distributed while being more isolated from CERN than other current Tier 1 countries**
**US Tier 1 must be augmented by additional capacity  (****particularly for *****analysis*****)**
**Appropriate US facilities level is ~ 2 x canonical Tier 1**

- B. Gibbard

- 26 October, 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 of comparable aggregate capacity**
**This model will ...**
**exploit high performance US regional networks**
**leverage existing resource at Tier 2 sites**
**establish architectural support for the inclusion of institutional resources at other (non-Tier 2) sites**
**focus on *****analysis*****: both increasing capacity and encouraging local autonomy and creativity within the analysis effort**

- B. Gibbard

- 26 October, 2000

## Schematic of Model

- B. Gibbard

- 26 October, 2000

## Facilities WBS

- B. Gibbard

- 26 October, 2000

## Tier 1 (WBS 2.3.1)

**US ATLAS Tier 1 is now operational with significant capacities at BNL in coordinating with the RHIC Computing Facility (RCF) **
**There is broad commonality in requirements between ATLAS and RHIC and long term synergy with RCF is expected**
**Personnel and cost projections for US ATLAS facilities are heavily base on recent experience at RCF ... *****see Rich Baker’s talk***

- B. Gibbard

- 26 October, 2000

##  Tier 1 (continued)

**Full Tier 1 Functionality Includes ...**
**Dedicated High Bandwidth Connectivity to CERN **
**Primary Site for Storage/Serving**
**Cache/Replicate 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

- 26 October, 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

- 26 October, 2000

## Tier 2 (continued)

**Developmental Phase**
**1****st****  Tier 2 will be selected and receive initial funding this year, FY ’01**
**2****nd**** Tier 2 will receive initial funding in FY ’02**
**These 2 developmental Tier 2 sites will participate in 2003 ATLAS MDC 2**
**Deployment Phase**
**Remaining 3 Tier 2’s will be selected on the basis of a single proposal process in 2003 and will receive initial funding in 2004**
**All Tier 2’s will be fully operational for 2006**
***See Rob Gardner’s talk***

- B. Gibbard

- 26 October, 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 should be practical by 2005**
**While the network is a integral part of the US ATLAS plan, its funding is not part of the US ATLAS budget**

- B. Gibbard

- 26 October, 2000

## WAN Configurations

- B. Gibbard

- 26 October, 2000

## US ATLAS Capacities

- B. Gibbard

- 26 October, 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

- 26 October, 2000