A conceptual model of grid resources and services

Authors:Sergio Andreozzi

Massimo SgaravattoCristina Vistoli

Presenter: Sergio AndreozziINFN-CNAF

Bologna (Italy)sergio.andreozzi@cnaf.infn.it

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OUTLINE

Short introduction to the GLUE activity GLUE Schema overview

– The conceptual model– The implementation status– Deployment roadmap

Related works Open issues

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GLUE: WHAT

GLUE: Grid Laboratory Uniform Environment collaboration effort focusing on interoperability

between US and EU HENP Grid middlewares Targeted at core grid services

– Resource Discovery and Monitoring– Authorization and Authentication – Data movement infrastructure– Common software deployment procedures

Preserving coexistence for collective services

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GLUE: WHO and WHEN

Promoted by DataTAG and iVDGL projects

Activity started in April 2002 considering as first step common information service schema between EU and US HENP Grid projects

Important contributions from the following projects: DataGrid, Globus, GriPhyN, PPDG, SRM

Main contributors (in alph order): J.Gordon, C.Kesselman, P.Kunstz, J.McGee, R.Pordes, A.Shoshani, J.Schopf, B.Tierney

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GLUE Schema overview 1/2

Conceptual model of grid resources to be used by the Grid Information Service for discovery and monitoring purposes

Based on the experience of DataGrid and Globus schema proposals

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GLUE Schema overview 2/2

Conceptual model – version 1.0 Finalized in Oct ’02 Model of computing resources (Ref. CE) Model of storage resources (Ref. SE) Model of relationships among them (Ref. Close

CE/SE) Currently working on version 1.1

Extensions Model of network resources

Possible other adjustements will come from experience (e.g. DataGrid v.2.0)

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GLUE Computing resources requirements

Separation between services and resources that implement it

Needs for both detailed host info (monitoring issue) and aggregate view (discovery issue)

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GLUE Computing Element

Computing Element: entry point into a queuing system– There is one computing element per queue of

a local resource management system– The information associated with a computing

element is limited only to information relevant to the queue

– All information about the physical resources accessed by a queue is represented by the Cluster information element

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GLUECluster/Subcluster/Host

Cluster: container that groups together subclusters or hosts.  A cluster may be referenced by more than one computing element

Subcluster: collection of “homogeneous” hosts:– All hosts of a subcluster have the same value for the

set of asserted attributes   Host: characterizes the configuration of a

computing node (e.g. processor, main memory, software)

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Computing Resources in GLUE

ComputingElement

ComputingElement

ComputingElement

ComputingElement

ComputingElement

ComputingElement

subcluster2subcluster1

Cluster 1

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GLUEStorage Service/Space/Library

Storage Service:– grid service identified by a URI that manages disk and

tape resources in term of Storage Spaces– all hardware details are masked– the Storage Service performs file transfer in or out of

its Storage Spaces using a specified set of third part data movement services (e.g. GridFTP)

– files are managed with respect to the lifetime policy specified for the Storage Space where they are kept

a specific date and time lifetime policy can be specified for each file and this is applied against a compatibility rules table

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GLUEStorage Service/Space/Library

Storage Space: portion of a logical storage extent identified by: – an association to a directory of the

underlying file system (e.g. /permanent/CMS)

– a set of policies (MaxFileSize, MinFileSize, MaxData, MaxNumFiles, MaxPinDuration, Quota)

– an association to access control base rules

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GLUEStorage Service/Space/Library

Storage Library: the machine providing for both storage space and storage service

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GLUEStorage Service/Space/Library

Storage LibraryArchitecture type + file system + files

Storage Serviceprotocol info

Storage SpaceStatus, Policies, Access Rules

Directory

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Computing/Storage Services relationships in Glue

The problem:– Job executed on Computing Elements (CEs)– Job may access files stored in Storage Space– Several replicas of these files can be spread over

the grid– The best replica is CE-dependent– Which strategy to assign the job to a CE and select

the best replica for it? Current solution:

– Computing-Storage Services association statically defined by SiteAdmin’s

– When the network resource model will be in place, this association could be dynamically defined

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GLUE SchemaImplementation status

Implementation status For Globus MDS 2.x:

LDAP Schema (DataTAG WP 4.1) Info providers for both computing and storage

resources

For EDG R-GMA: Relational model implementation (DataGrid, both

schema and information providers)

For Globus OGSA: XML Schema (Globus)

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Deployment roadmap

– In DataTAG, a mixed testbed already in place with: EDG 1.4.x (+ Glue) nodes in Italy LCG-0 node at CERN VDT nodes in US (FNAL, Indiana University)

– CMS, ATLAS and ALICE experiment suites already successfully integrated with EDG Resource Broker, Glue schema based

– Grid middleware distributions and the Glue schema Already included in

– VDT 1.1.7– LCG-0

Will be soon included in – EDG 2.0– Globus 2.2.x

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Related works

EDT-LCG Monitoring collaboration:– development of a Grid monitoring tool in order to

monitor the overall functioning of the Grid– Will be presented here at CHEP

Today, parallel session 1b-Monitoring, 4.50 PM

Network resource modeling: – Definition of a network model that enables an efficient

and scalable way of representing the communication capabilities between grid services for brokering activity

– Will be presented here at CHEP: next Thursday, parallel session 1b–Monitoring, 4.10 PM

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Main open issues

– Computing: refine aggregated view of a cluster from the

queue viewpoint

– Storage: Gain better understanding of Storage Service,

when mapping a disk space access or an SRM service

– High Level Grid Services, define a general grid service

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REFERENCE

DataTAG Project– http://www.datatag.org

Grid Laboratory Uniform Environment (GLUE) DataTAG WP4 and iVDGL Interoperability Group version 0.1.2

– http://www.hicb.org/glue/glue-v0.1.2.doc GLUE Schema documents

– http://www.cnaf.infn.it/~sergio/datatag/glue EDT-LCG Monitoring

– http://gridmon.na.infn.it/lcg-edt GGF CIM Grid Schema WG

– http://www.isi.edu/~flon/cgs-wg/