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The Sequential Access Model for Run II Data Management and Delivery

The Sequential Access Model for Run II Data Management and Delivery. Lee Lueking , Frank Nagy, Heidi Schellman, Igor Terekhov, Julie Trumbo, Matt Vranicar, Rich Wellner, Vicky White. URL: www-d0.fnal.gov/~lueking/sam/sequential.html. CHEP98 Sept. 3, 1998.

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The Sequential Access Model for Run II Data Management and Delivery

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  1. The Sequential Access Model for Run II Data Management and Delivery Lee Lueking, Frank Nagy, Heidi Schellman, Igor Terekhov, Julie Trumbo, Matt Vranicar, Rich Wellner, Vicky White. URL: www-d0.fnal.gov/~lueking/sam/sequential.html. CHEP98 Sept. 3, 1998

  2. What is The Sequential Access Model: SAM? • Sequential events: Data is stored in files as sequential events. • Data Tiers: Each event is stored in each of several data tiers. • The Event Data Unit (EDU) is the unit of data stored in each tier. • Physical event size: EDU5=5kB/event, EDU50=50kB/event, et cetera. • Physical streaming (clustering): Data categories based on Trigger or reconstruction information • Database catalog: File, Event and Processing Database; Information about the data - event-level, file-level, run-level. Also processing information; static and dynamic.

  3. Data Organization User and physics group (derived) data File & Event Database Event Information Tiers Warm Cache Physical Clustering

  4. How Do I Access Data? • Pipelines: Data access channels tailored for particular processing and analysis patterns. • Pipeline segments: Tapes, drives + Automated Tape Library + Storage Management System, network, group-shared and/or user-private analysis disk. • Example access modes: • Database:Access to event, trigger & other FEDB info. • Thumbnail: Disk resident sketch of each event. • Freight Train: Large data stream file server. • Event Picking: Random event selection from any data tier. • Small Data-set:One or a few files from any data tier.

  5. Data Access Mass Storage Pipeline Consumers File&EventDB Thumbnail Freight Train Pick Event User File =Group of Users =Data flow =File =Disk Storage =Tape Storage =Pipeline Name =Single User =Event File&EventDB

  6. D0 Specifications • Data sizes • Further details • 10-15 exclusive streams preferred. Based on L3 and/or Reconstruction information. • 10% warm (tape or disk) caches of Raw and Medium EDU data. • Possible on-demand reconstruction.

  7. Will SAM Scale to Run II?

  8. Exclusive Streaming See Talk #182: Heidi Schellman, “Assurance of Data Integrity in a Petabyte Data Sample”

  9. Data Handling System Buffer and Cache

  10. SAM Design Details • Network distributed. • Easily scalable. • Works for all access modes. • Uses CORBA interfaces between modules. • Modules being written in JAVA, Python and C++. • File, Event and Processing Database uses ORACLE 8. • Not tightly coupled to: • Tape Mass Storage System. • CPU availability or Batch processing facilities on Farm or Analysis machines. • The D0 event data model.

  11. Main Components • File and Event Database: Info about data location and processing details. (see poster session #127: Vicky White, “Use of ORACLE in Run II for D0” ) • Global Optimizer: Optimizes tape access and regulates bandwidth to various stations and activities. • Station: Management for a set of processing resources, including buffer and Data I/O. • Project Master: Responsible for managing projects which are lists of files to process. • Consumer/producer: Actual data processing • GUI and API user interfaces: Allow users to access data and administrators to control the system.

  12. Components of SAM Consumer/ Producer User & Admin. Interface (API and GUI) Consumer/ Producer Station F Consumer/ Producer Station A Station E Consumer/ Producer Project Master DB and Information Servers Mass Storage System Consumer/ Producer Global Optimizer Station D Station B Station C

  13. File and Event Database Run Volume Data Tier Events ID Event Number Trigger L1 Trigger L2 Trigger L3 Off-line Filter Thumbnail Files ID Name Format Size # Events Physical Data Stream Trigger Configuration Project Event-File Catalog Processing Info

  14. (Mass Storage System Needs) • Provide access to data through file-level semantics. • Manage all tape activity within the ATL(S) and to/from shelf. • Allow data to be physically clustered in tape groupings or “file families”. • A mechanism for sending priorities with file requests to allow control over allocation of resources for various activities. • System must optimize the use of resources such as arm time and tape mounts. • Retry and fail-over features for failed tape read/write activities. • Open tape format to allow removal of tapes and exchange of data with other sites. • Reliable and unattended operation. See ENSTORE presentation #126: Don Patravic, “ENSTORE - An Alternative Data Storage System”

  15. Access to Data through SAM • User or group defines a “project” by sending a list of constraints or file list to the Database Server. • DB Server returns a summary of the project (number of files, size and availability). • User is provided a list of possible “stations” where the project might run. He chooses one. • User registers with the station for a given (new or existing) project. He is given a unique “key” to use. • User’s client “consumer/ producer” sends the “project master” on the chosen station the “key”, and is given the next available file in the “project”.

  16. Consumer- Read from Storage

  17. Producer - Write to Storage

  18. SAM Prototype • Status: Being built, ready early October. • Goals: • Populate and exercise the SAM database. • Specify projects - data to be accessed for processing or analysis. • Attach to a ‘Station’ which makes files for that Project accessible. • Interface to ENSTORE - get/put files - using SAM “Global Optimizer”. • Build Analysis programs using D0 framework. • Demonstrate multiple Stations, Projects, Analysis consumers . • Testing: Further testing in fall with SAM PC test-bed. • Beta version: Plan to make MC data available through SAM late ‘98.

  19. SAM Prototype PC test-bed Example configuration Enstore Warehouse Network HUB SAM Station Servers Consumers/Producers Main Backbone To Database Server

  20. Summary • Dzero plans to use a file based Sequential Access Model for run II data access. • The design is network distributed with CORBA communication between modules written in JAVA, PYTHON and C++. ORACLE 8 is used for the DB. • A SAM prototype is being built now and will be ready in Early October. • Hardware to construct a SAM test-bed will be assembled this fall to more fully test and understand the system. • We plan to employ the system for MC data by the end of `98, and perform large-scale testing with Run II hardware the first part of next year.

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