1. FESR www.trigrid.it Trinacria Grid Virtual Laboratory gLite Information System Muoio Annamaria INFN - Catania gLite 3.0 Tutorial Trigrid Catania, 27-28.07.2006

2. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 2 Information System What is? –System to collect information on the state of resources Why? –To discover resources of the grid and their nature –To have useful data in order to who is in charge of managing the workload to do it more efficiently. –To check for health status of resources. How? –Monitoring state of resources locally and publishing fresh data on the information system. –Adopting a data model that MUST be well known to all components that want to access monitored information –Using different approaches that we are going to investigate in the next slides

3. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 3 Design of Information Systems About Measures –Measures SHOULD be sensitive to the aim the users want to achieve. –Measures SHOULD be enough accurate to be considered valid. –Rate of taking measures MUST be adequate to be used. About the gathering of Information –How and when collected info should be published? –Where should collected info be stored? –How long should this info be maintained in the storage? Querying the Information System –Where should queries be sent to have a response? –What syntax and protocols have to be adopted to make queries? –What is the adopted data model to describe resources? Security –Who is allowed to execute queries against the IS and what type of queries is he allowed to do? –Management of user rights and credentials.

4. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 4 Adopted Information Systems The BDII (Berkeley DB Information Index) –has been adopted in LCG middleware as the Information System provider. –It is an evolution of the Globus Meta Directory System (MDS) –LCG-2 actually adopts BDII as Information System. –It is based on Lightweight Directory Access Protocol (LDAP) servers. The Relational Grid Monitoring Architecture (R-GMA) –Is an implementation of the Grid Monitoring Architecture (GMA) standardized by the Global Grid Forum (GGF) –It is a relational implementation of the GMA –It is strongly Web Services Oriented –It uses standard SQL query syntax

5. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 5 LCG Information System LCG adopts a combination of solutions –Globus MDS  At the lowest level of the information system  To discover and monitor resources and publish information  Grid Information Security (GSI) credentials  Caching –BDII  At the highest level of the system  Because MDS had some troubles in terms of scalability  Used by the Resource Broker for the matchmaking process  Can be configured by each VO  Queries underlying systems periodically (2 minutes) Hierarchical system –Information is collected on the leaves of a hierarchical tree and travels towards the root –Clients can query the hierarchical tree at every level –The higher the level against which queries are made, the older is the obtained information

6. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 6 Collecting Information Gathering of information at different levels –Lower level: Grid Resource Information Server (GRIS)  Collects information on the state of a given resource  One GRIS on top of each resource  A set of scripts and sensors that try to extract useful info on the resource –Medium level: Grid Index Information Server (GIIS)  Collects information on resources of a given site  One GIIS for each site –Higher level: BDII  Collects information on resources of a given VO  One BDII for each VO (suggested solution) Way of collecting info –Pull model (higher level servers periodically query lower level servers) –LDAP query model

7. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 7 BDII The Berkeley Database Information Index (BDII) –Developed within the context of LCG project –Solves problems of instability of the MDS occurring when the number of sites grows too much –Stays on top of GIIS sites –One for each VO –Centralized system –Three levels of hierarchy –Accessed by the Workload Management System Way of working –One GRIS for each resource –One GIIS for each site collecting info from below GRIS systems –One BDII for a given VO collecting information from below GIIS systems –Two LDAP servers, one for write access and one for read access –Every two minutes a cron-job runs a script and collects info from a list of GIIS sites –The list of GIIS is placed in the configuration file of the BDII

8. To change: View -> Header and FooterCatania, glite 3.0, 27-28.07.2006 8 Link wiki Now we are connected to this link and we proceed with the practicals: https://grid.ct.infn.it/twiki/bin/view/GILDA/UserTutorials