NOAO Brown BagTucson, AZ

March 11, 2008

Jeff KantorLSST Corporation

Requirements Flowdown with LSST

SysML and UML Models

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March 11, 2008 Tucson, AZ

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Presentation Outline

• LSST Data Management introduction• Requirements flow-down• Enterprise Architect SysML/UML demonstration

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Data Management is a distributed system that leverages world-class facilities and cyber-infrastructure

Long-Haul CommunicationsChile - U.S. & w/in U.S.

2.5 Gbps avg, 10 Gbps peak

Archive Center

NCSA, Champaign, IL

100 to 250 TFLOPS, 75 PB

Data Access CentersU.S. (2) and Chile (1)45 TFLOPS, 87 PB

Mountain Summit/Base FacilityCerro Pachon, La Serena, Chile

25 TFLOPS, 150 TB

1 TFLOPS = 10^12 floating point operations/second

1 PB = 2^50 bytes or ~10^15 bytes

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LSST Data Management provides a unique national resource for research & education

• Astronomy and astrophysics– Scale and depth of LSST database is unprecedented in astronomy

• Provides calibrated databases for frontier science• Breaks new ground with combination of depth, width,

epochs/field• Enables science that cannot be anticipated today

• Cyber-infrastructure and computer science– Requires multi-disciplinary approach to solving challenges

• Massively parallel image data processing• Peta-scale data ingest and data access• Efficient scientific and quality analysis of peta-scale data

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DM system complexity exists but overall is tractable

• Complexities we have to deal with in DM– Very high data volumes (transfer, ingest, and especially query)– Advances in scale of algorithms for photometry, astrometry, PSF

estimation, moving object detection, shape measurement of faint galaxies– Provenance recording and reprocessing– Evolution of algorithms and technology

• Complexities we DON’T have to deal with in DM– Tens of thousands of simultaneous users (e.g. online stores)– Fusion of remote sensing data from many sources (e.g. earthquake

prediction systems)– Millisecond or faster time constraints (e.g. flight control systems)– Very deeply nested multi-level transactions (e.g. banking OLTP systems)– Severe operating environment-driven hardware limitations (e.g. space-

borne instruments)– Processing that is highly coupled across entire data set with large amount

of inter-process communication (e.g. geophysics 3D Kirchhoff migration)

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Performance - Nightly processing timeline for a visit meets alert latency requirement

Exposure 1

Exposure 2

Shutterclose

Time(sec)

Readoutcomplete

Transfer to Basecomplete

Image Processing/ Detection complete

Associationcomplete

Alert generatecomplete

Shutterclose

Readoutcomplete

Transfer to Basecomplete

Image Processing/Detection complete

2s 6s 20s

Exposurebegins

15s

T0 - Start of 60 second latency timer

3s6s 20s 10s 10s

T0 + 51s

2s

Exposurebegins

15s

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ArchiveCenter

Base

Data AccessCenter Archive Center

Trend Line

Computing needs show moderate growth

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Database Size (data+indexes, cumulative)

0

2

4

6

8

10

12

14

16

2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024

year

PB

Database Volumes

• Detailed spreadsheet-based analysis done• Expecting:

– 6 petabytes of data, 14 petabytes data+indexes

– all tables: ~16 trillion rows (16x1012)

– largest table: 3 trillion rows (3x1012)

Database Size (data only, per table, cumulative)

0

1

2

3

4

5

6

2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024year

PB

DIASource-stars

DIASource-galaxies

Source-stars

Source-galaxies

VarObj-stars

VarObj-galaxies

Objects-stars

Objects-galaxies

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CerroPachonLa

Serena

Long-haul communications are feasible

• Over 2 terabytes/second dark

fiber capacity available

• Only new fiber is Cerro Pachon

to La Serena (~100 km)

• 2.4 gigabits/second needed from

La Serena to Champaign, IL

• Quotes from carriers include 10

gigabit/second burst for failure

recovery

• Specified availability is 98%

• Clear channel, protected circuits

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ScienceRequirements

Document

Telescope, Camera, Survey

Reference Designs

Data Management

Requirements

Data ManagementDesign

Complete, traceable flow-down from scienceto system, to data management subsystem

Allocation

Traceability

DMS Sizing Models:

Processing, Storage,

Communications

Allocation

Traceability

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ScienceRequirements

Document

SystemRequirements,

Telescope, Camera,Survey

Reference Designs

Key Specified and Derived Requirements

• The mission, instrument design, observing cadence and observatory operational requirements drive the DM requirements Data

ManagementRequirements

Data ManagementDesign

Data Products• Images• Catalogs• Alerts• Quality and Performance

StatisticsAlgorithms/Pipelines• Astrometric/Photometric

Calibration• Source Detection• Source - Object Association• Moving Object

Detection/Orbit Matching• Alert Processing• Deep Detection• Calibration• ClassificationArchitectural• Scalabiity• Reliability/Availability• Evolution

Science and system requirements flow-down using SysML

Allocation

Traceability

System Modeling Language

(SysML)

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DMS Sizing ModelsComputational Requirements Processing

• Sustained & peak processing analyzed• Tradeoffs considered:

• Store vs. recompute• Types of parallelism• Reliability vs cost

Storage• Sustained & peak I/O rates and storage needs analyzed• Tradeoffs considered:

• Store vs. recompute• DBMS vs File System• Multi-dimensional access• Reliability vs cost

Communications• Sustained & peak bandwidth analyzed• Tradeoffs considered:

• Transfer and process vs process and transfer• Media transfer vs network• Reliability vs cost

Data ManagementRequirements

Data Management

Design

Storage and Input/Output Requirements

Data Transfer,Replication, And Access

Requirements

Performance requirements analyzed & feasible

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Systems Engineering Model for Requirements Flowdown, Traceability & Configuration Control

SysML = System Modeling Language

SE Model

Operational Model

Structural/Component Model

Requirements Model

Other Engineering Analysis Models

Performance & Constraints Model

FEMAPNX Nastran

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Requirements Flow

SRD

TelescopeSite Req.

CameraReq.

DataManagement

Req.

Functional Req.(FPRD)

Operational Req.(OCDD)

InterfaceRequirements

OutsideConstraints

System Requirements

SysMLModel

DMSubsystems

Req.

UML Model

T&SSubsystems

Req.

SysML Model

CameraSubsystems

Req.

LSST Board&

Science Council

Project OfficeChange Control

Board

Project OfficeChange Control

Board

SubsystemGroup

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Requirements Hierarchy

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Rigorous process for software engineeringbased on wide industry experience (Iconix)

Algorithm/Pipeline Data Product Prototypes

Image courtesy of Iconix Software Engineering, Inc. Unauthorized use not permitted.

Unified Modeling Language (UML)

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Demo of Enterprise Architect Tool for SysML and UML

System Engineering (SysML model is in “DM SysML.pdf”)

Science RequirementsDM Functional/Performance Requirements

Use Cases

Software Engineering (UML model is in “DM UML.pdf”)

Use Cases/Robustness DiagramsClass Diagrams/Sequence Diagrams

Code