THE REPLICA LOCATION SERVICEThe Globus Project and the DataGrid Project
Consistent state maintained in Local Replica Catalogs (LRCs)• Mappings between logical names (LFNs) and target names
Collective state with relaxed consistency in Replica Location Indices (RLIs)• Each RLI contains mappings from LFNs to LRCs• Variety of index structures can be created by varying number of RLIs, redundancy and partitioning
Soft state maintenance of RLI state• LRCs send state information to RLIs using soft state protocols• Information in RLIs times out and must be periodically refreshed
Optional compression of soft state updates• Prototype implements Bloom filter compression
Membership service • Keeps track of LRCs and RLIs and their soft state update patterns• Prototype implements static configuration for RLS
Five Components of the RLS Architecture Framework
Front-End Server • Multi-threaded• Supports GSI Authentication• Common implementation for LRC and RLI
Back-end Server• mySQL Relational Database • Holds logical name to target name mappings
Client APIs: C and Java
RLS Components
The RLS Implementation
LRC LRC LRC LRC
RLI RLI RLI
Replica Location Index Nodes
Local Replica Catalogs
The RLS SC2002 Testbed
The Replica Location Service Architecture
Replication in Data Grids
RLS Designers and Developers RLS Sponsors and Testbed ParticipantsGlobus Project: www.globus.org/rls
Shishir Bharathi, Ann Chervenak, Ewa Deelman, Ian Foster, Carl Kesselman, Matei Ripeanu, Bob Schwartzkopf, Mei-Hui Su
DataGrid Project: http://cern.ch/grid-data-management
Leanne Guy, Peter Kunszt, Heinz Stockinger, Kurt Stockinger
Two types of soft state updates from LRCs to RLIs• Complete list of logical names registered in LRC• Bloom filter summaries of LRC
Bloom filter advantages • Reduce size of soft state updates• Reduce associated memory and network requirements• Sending updates is faster and scales better with size of LRC
User-defined attributes • May be associated with logical or target names
Partitioning• Divide LRC soft state updates among RLI index nodes using pattern matching of logical names
Redundancy• Send soft state updates to multiple RLIs
Implementation Features
Large data sets are frequently replicated to:• Reduce access latency• Maintain local control over necessary data• Improve reliability and load balancing
A Replica Location Service is a distributed registry service that records the locations of data copies and allows discovery of replicas
possum
emu
wombat
koala
Melbourne
RLIs
LRCs
n16
n19
n17
n18
dc-n1
dc-n4
dc-n2
dc-n3
a33
a36
a34
a35
rls01
rls02
rls02
rls01
ANL(Chicago)
ISI(Los Angeles)
SC2002(Baltimore)
SLAC(Palo Alto)
Replica Location Index Nodes
Local Replica Catalogs
0342
pcr25
0343
pcr24
0344
grid03
0345
grid01
0346 grid8 grid6
grid7.mi
grid1
grid7.pi
CERN(Geneva)
Glasgow INFN(Pisa)
INFN(Milan)
Replica Location Index Nodes
Local Replica Catalogs
Australia Sites Unites States Sites Europe Sites
DB
LRC/RLI Server
ODBC (libiodbc)
myodbc
mySQL Server
clientclient
