Transcript Document

Data management in grid.
Comparative analysis of
storage systems in WLCG.
Really Two Data Problems
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The amount of data
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High-performance tools needed to manage the huge raw volume of
data
• Store it
• Move it
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Measure in terabytes, petabytes, and ???
The number of data files
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High-performance tools needed to manage the huge number of
filenames
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1012 filenames is expected soon
Collection of 1012 of anything is a lot to handle efficiently
Data Questions on the Grid
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Questions for which you want Grid tools
to address
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Where are the files I want?
How to move data/files to where I want?
Data intensive applications
• Medical and biomedical:
– Image processing (digital
X-ray image analysis)
– Simulation for radiation
therapy
• Climate studies
• Physics:
– High Energy and other
accelerator physics
– Theoretical physics, lattice
calculations of all sorts
• Material sciences
LHC as a data source
500 MB/sec
15 PB/year
15 years
A Model Architecture for Data
Grids
Metadata
Catalog
Attribute
Specification
Application/
Data Management
System
Logical Collection and
Logical File Name
Selected
Replica
SRM commands
Replica
Catalog
Multiple Locations
Replica
Selection
MDS
Performance
Information and
Predictions
Disk Cache
Tape Library
Disk Array
Replica Location 1
Disk Cache
Replica Location 2
Replica Location 3
SRM: Main concepts
– Space reservations
– Dynamic space management
– Pinning file in spaces
– Support abstract concept of a file name: Site URL
– Temporary assignment of file names for transfer: Transfer URL
– Directory management and authorization
– Transfer protocol negotiation
– Support for peer to peer request
– Support for asynchronous multi-file requests
– Support abort, suspend, and resume operations
– Non-interference with local policies
Storage properties
• Access Latency (ONLINE, NEARLINE,
OFFLINE)
• Retention Policy (REPLICA, OUTPUT,
CUSTODIAL)
Use cases
Access Latency (ONLINE, NEARLINE, OFFLINE)
Retention Policy (REPLICA, OUTPUT, CUSTODIAL)
Logical File Name (LFN)
Also called a User Alias,
In case the LCG File Catalog is used the
LFNs are organized in a hierarchical
directory-like structure, and they will have
the following format:
lfn:/grid/<MyVO>/<MyDirs>/<MyFile>
Site URL and Transfer URL
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Provide: Site URL (SURL)
– URL known externally – e.g. in Replica Catalogs
– e.g. srm://ibm.cnaf.infn.it:8444/dteam/test.10193
Get back: Transfer URL (TURL)
– Path can be different from SURL – SRM internal mapping
– Protocol chosen by SRM based on request protocol preference
– e.g. gsiftp://ibm139.cnaf.infn.it:2811//gpfs/sto1/dteam/test.10193
One SURL can have many TURLs
– Files can be replicated in multiple storage components
– Files may be in near-line and/or on-line storage
– In a light-weight SRM (a single file system on disk) SURL may be the
same as TURL except protocol
Third party transfer
• Controller can be separate from src/dest
Client
Control channels
Site B
Site A
Server
Server
Data channel
July 11-15. 2005
Lecture 4: Grid Data Management
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Going fast – parallel streams
• Use several data channels
Control channel
Site B
Site A
Server
July 11-15. 2005
Data channels
Lecture 4: Grid Data Management
13
Interoperability in SRM v2.2
dCache
BeStMan
Be r k e l e y
Disk
CASTOR
DPM
SRM
Client
User/application
xrootd
BNL
SLAC
LBNL
SRB
(iRODS)
SDSC
SINICA
LBNL
EGEE
Total Online Space Share
Popularity
CASTOR Architecture
CUPV
VDQM
server
VDQM
server
NAME
server
NAME
server
RFIO
Client
STAGER
RTCPD
TPDAEMON
(PVR)
RTCPD
(TAPE
MOVER)
RFIOD
(DISK
MOVER)
DISK POOL
VOLUME
manager
MSGD
Basic dCache Design
DPM
-- DPM config
-- All requests
(SRM, transfers…)
-- Namespace
-- Authorization
-- Replicas
DPM Database
DPNS Database
Client
Standard
Storage
Interface
Very important
to backup !
SRM Daemon
DPNS Daemon
Data Server
Gridftp Daemon
Rfio Daemon
DPM Daemon
Can all be installed
on a single machine
Data Server
Gridftp Daemon
Rfio Daemon
Data Server
Gridftp Daemon
Rfio Daemon
Store physical files
EOS: What is it ...
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Easy to use standalone disk-only storage for user
and group data with in-memory namespace
– Few ms read/write open latency
– Focusing on end-user analysis with chaotic access
– Based on XROOT server plugin architecture
– Adopting ideas implemented in Hadoop, XROOT,
Lustre et al.
– Running on low cost hardware
• no high-end storage
– At CERN: Complementary to CASTOR
EOS: Access Protocol
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EOS uses XROOT as primary file access protocol
– The XROOT framework allows flexibility for
enhancements
• Protocol choice is not the key to performance as
long as it implements the required operations
– Client caching matters most
• Actively developed, towards full integration in ROOT
(rewrite of XRootD client at CERN)
• SRM and GridFTP provided as well
– BeStMan, GridFTP-to-XROOT gateway
Thank you
Grid, Storage and SRM. OSG
Managed Data Storage and Data Access Services for Data Grids. M. Ernst,
P. Fuhrmann, T. Mkrtchyan DESY
J. Bakken, I. Fisk, T. Perelmutov, D. Petravick Fermilab
dCache. Dmitry Litvintsev, Fermilab. OSG Storage Forum, September 21,
2010
GridFTP: File Transfer Protocol in Grid Computing Networks. Caitlin Minteer
Light weight Disk Pool Manager status and plans. Jean-Philippe Baud, ITGD, CERN
Storage and Data Management in EGEE, Graeme A Stewart1, David
Cameron, Greig A Cowan and Gavin McCance
and many others