Gridifying the LHC Data

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Gridifying the LHC Data

• Peter Kunszt
• CERN IT/DB
• EU DataGrid Data Management
• Peter.Kunszt_at_cern.ch

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Outline

• The Grid as a means of transparent data access
• Current mode of operations at CERN
• Elements of Grid data access
• Current capabilities of the EU DataGrid/LCG-1
  Grid infrastructure
• Outlook

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Outline

• The Grid as a means of transparent data access
• Current mode of operations at CERN
• Elements of Grid data access
• Current capabilities of the EU DataGrid/LCG-1
  Grid infrastructure
• Outlook

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The Grid vision

• Flexible, secure, coordinated resource sharing
  among dynamic collections of individuals,
  institutions, and resource
• From The Anatomy of the Grid Enabling Scalable
  Virtual Organizations
• Enable communities (virtual organizations) to
  share geographically distributed resources as
  they pursue common goals -- assuming the absence
  of
• central location,
• central control,
• omniscience,
• existing trust relationships.

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Grids Elements of the Problem

• Resource sharing
• Computers, storage, sensors, networks,
• Sharing always conditional issues of trust,
  policy, negotiation, payment,
• Coordinated problem solving
• Beyond client-server distributed data analysis,
  computation, collaboration,
• Dynamic, multi-institutional virtual
  organizations
• Community overlays on classic organization
  structures
• Large or small, static or dynamic

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Grid middleware architecture hourglass

• Current Grid architectural functional blocks

ALICE
ATLAS
CMS
LHCb
Specific application layer
LCG
Common application layer
EU DataGrid middleware
Advanced Grid Services
Basic Grid Services
GLOBUS 2.2
OS, Storage Network services
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Grid Middleware Cloud
Authentication, Authorization Requirement
parsing Resource matching Resource
allocation Accessibility
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Vision of Grid Data Management

• Distributed Shared Data Storage
• Ubiquitous Data Access
• Transparent Data Transfer and Migration
• Consistency and Robustness
• Optimisation

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Vision of Grid Data Management

• Distributed Shared Data Storage
• Different architectures
• Heterogenous data stores
• Self-describing data and metadata

GRID
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Vision of Grid Data Management

• Ubiquitous Data Access
• Global Namespace
• Transparent security control and enforcement
• Access from anytime anywhere, physical data
  location irrelevant
• Automatic Data Replication and Validation

GRID
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Vision of Grid Data Management

• Transparent Data Transfer and Migration
• Protocol negotiation and multiple protocol
  support
• Management of data formats and database versions

GRID
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Vision of Grid Data Management

• Consistency and Robustness
• Replicated data is reasonably up-to-date
• Reliable data transfer
• Self-detecting and self-correcting mechanisms
  upon data corruption

GRID
?
X
?
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Vision of Grid Data Management

• Optimisation
• Customisation or self-adaptation to specific
  access patterns
• Distributed Querying, Data Analysis and Data
  Mining

GRID
!
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Existing Middleware for Grid Data Management -
Overview

• Globus
• GridFTP
• Replica Catalog
• Replica Manager
• EU DataGrid
• GDMP
• Replica Catalog
• Replica Manager
• Spitfire
• Condor
• NeST

• PPDG
• Magda
• JASMine
• GDMP
• SAM
• Griphyn/iVDGL
• Virtual Data Toolkit
• Storage Resource Broker
• Storage Resource Manager
• ROOT
• Alien
• Nimrod-G
• Legion

Not exhaustive
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What you would like to see
reliable available powerful calm cool easy to use
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Outline

• The Grid as a means of transparent data access
• Current mode of operations at CERN
• Non-Grid operations
• Grid operations
• Elements of Grid data access
• Current capabilities of the EU DataGrid/LCG-1
  Grid infrastructure
• Outlook

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Current non-Grid Operations (Oversimplified)
Fabric
Storage
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Current non-Grid Operations

• Planning of
• Resources (computing and storage)
• Projects and job schedules
• Data placement
• Monitoring of
• Running jobs
• Available resources
• Alarms

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Grid Testbed Today

• Currently largest Grid Testbed EU DataGrid
• Not a full-fledged Grid fulfilling the Grid
  vision
• Pragmatic what can be done today
• Research aspect trying out novel approaches
• Operation of each Grid Site
• Huge effort at each computing center for
  installation and operations support
• Local user support is necessary but not
  sufficient
• Operation of the Grid as a logical entity
• Complex management coordination effort among
  Grid centers concerning Grid middleware updates,
  but also policies, trust relationships
• Grid middleware support through many channels
• Complex interdependencies of Grid middleware

See talk in the afternoon
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Outline

• The Grid as a means of transparent data access
• Current mode of operations at CERN
• Elements of Grid data access
• Current capabilities of the EU DataGrid/LCG-1
  Grid infrastructure
• Outlook

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Grid Data Access ElementsStorage and Transfer

• Grid Storage Resource Manager
• Managed storage
• GSI enabled
• Mass Storage System interface
• Grid accessible Relational Database
• Data transfer mechanism between sites in place

Site 1
Site 2
Site 3
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Grid Data Access ElementsI/O

• Transfer protocols (gsiftp, https, scp)
• File System and/or Posix I/O for direct
  read/write of files from Worker Nodes
• SQL or equivalent interface to relational data
  from Worker Nodes

Storage
Posix or SQL Interface
Transfer Protocols
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Grid Data Access ElementsCatalogs

• Grid Data Location Service
• Find location of all identical copies (replicas)
• Metadata Catalogs
• File/Object specific metadata
• Logical names
• Collections
• Grid Database Object Catalog

catalog
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Higher Level Data Management Services

• Customizable pre- and post-processing services
• Transparent encryption and decryption of data for
  transfer and storage
• External catalog updates
• Optimization Services
• Location of the best replica based on access
  cost
• Active preemptive replication based on usage
  patterns
• Automated replication service based on
  subscriptions
• Data Consistency Services
• Data Versioning
• Consistency between replicas
• Reliable data transfer service
• Consistency between catalog data and the actual
  stored data
• Virtual Data Services
• On-the-fly data generation

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Outline

• The Grid as a means of transparent data access
• Current mode of operations at CERN
• Elements of Grid data access
• Current capabilities of the EU DataGrid/LCG-1
  Grid infrastructure
• Outlook

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File Names

• GUID Global Unique IDentifier
• guidf81d4fae-7dec-11d0-a765-00a0c91e6bf6
• LFN Logical File Name
• lfnpresentation
• LCN Logical Collection Name
• lcnstorage_workshop_presentations
• SFN Site File Name
• sfn//ccgridli02.in2p3.fr/edg/SE/dev/wpsix/higgs/d
  ata/123.ppt
• TURL Transport URL
• file///home/pkunszt/presentation.ppt
• https//storage.cern.ch/data/pkunszt/file4256.dat
• rfio//srm.cern.ch/castor/user/p/pkunszt/presentat
  ion.ppt
• gsiftp//pcrd24.cern.ch/data/pkunszt/pfn10_1.ppt

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Data Services in EDG/LCG1 Storage and I/O

• Grid Storage Element for files
• Understands SFNs maps into TURL
• GSI enabled interface Storage Resource
  Managerhttp//sdm.lbl.gov/srm/documents/joint.doc
  s/SRM.joint.func.design.part1.doc
• Support of different MSS backends
• Support for GridFTP and RFIO (CASTOR)
• Will be deployed this week in the EDG testbed for
  the first time.
• GridFTP Server for files
• only TURL (gsiftp//)
• Also GSI enabled
• Only FTP-like functionality, no management
  capabilities
• Current remote I/O
• NFS
• RFIO
• GridFTP

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Data Services in EDG/LCG1 Database access

• Spitfire
• Thin client for GSI-enabled database access
• Customizable, API exposed through a Web Service
  WSDL
• Not suitable for large result sets
• Not used by HEP applications yet

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Data Services in EDG/LCG1 Replica Location
Service RLS

• Distributed file catalog
• Stores GUID ? SFNmappings
• Stores replication metadata (e.g. file size,
  creator, MD5 checksum) on SFNs
• Local Catalogs hold the actual name mappings
• Remote Indices respond with the list of LRCs most
  probably having an entry on the file
• LRCs are configured to send index updates to any
  number of RLIs
• Indexes are Bloom Filters Implementation using
  Web Service Technology
• Scales well

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Data Services in EDG/LCG1 Replica Metadata
Catalog

• Single logical service for replication metadata
• Deployement possible as a high-availability
  service (Web service technology)
• Possibility of synchronized data on many sites to
  avoid a single site entry point (Using underlying
  database technology)
• Holds Logical File Name (LFN) ? GUID mappings
  (aliases)
• Contains LCN ? set of GUIDs mapping
  (collections)
• Holds replication metadata on LFNs, LCNs and
  GUIDs
• Might hold a small amount of replica-specific
  application metadata O(10) items

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Data Services in EDG/LCG1 Higher Level Services

• EDG Replica Manager ERM
• Coordinates all replication service
• Replica Optimization Service ROS
• Rely on Network Monitoring (iperf) between
  Testbed sites
• Rely on Storage Element access cost method
  (estimated time to stage a file)
• Summarize network costs for generic access
  requests
• Allows Replica Manager to choose best replica

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Replication Services Interactions
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Outlook

• We took only the first step on the long road to
  fulfilling the Grid vision
• Promising initial results but a lot of work still
  needs to be done
• Industry has only recently joined the Grid
  community through GGF industrial-strength
  middleware solutions are not available yet
• By the end of this year well have a first
  experience with a Grid infrastructure that was
  built for production from the start (LCG1).

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Open Grid Services Architecture

• OGSA is a framework for a Grid architecture based
  on the Web Service paradigm.
• Every service is a Grid Service. The main
  difference to Web Services is that Grid Services
  may be stateful services.
• These Grid Services interoperate through
  well-understood interfaces.
• The reference implementation, Globus Toolkit 3 is
  still in beta, the first release is expected for
  this summer.
• Depending on the evolution until the end of the
  year, we will see whether OGSA becomes stable
  enough to be considered for integration into LCG
  next year.

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• Thank you for your attention