Data Technologies-CERN School of Compuaing 2019 Data Technologes-CERN School of Computing 2019 Name Server Criticality of the name server performance .The name server is"the"database of a managed storage Every meta-data operation requires a database system which contains the catalogue of all data(typically transaction. all files) It is a simple lookup-based,single-key,database ◆It is essential to understand where the“name application for which several implementation exists server"approach is placed... DNS(domain name server)software The name server lookup time dictates the ◆LDAP databases performance of the whole storage system Hash tables /Object databases The database becomes the bottleneck of the Relational Databases entire storage process:low performances are a Name server reliability is critical symptom of major architectural mismatch Name server failure brings down the whole storage system Comment:Cloud storage An architecture that Name server performance is critical replaces the name server DB lookup with a ◆See next slide. "calculated"name resolution (..more to come...) Data Technologles-CERN School of Computing 2019 Short digression on.… Uniform Resource Identifiers(URI) Similar problem in storage systems ◆Example from the web. Example from storage... http://csc.cern.ch/data/2012/School/page.htm storage://cern.ch/data/2012/School/page.htm ↑ 个 ↑↑ ↑ ↑↑ protocol host/domain volume folder/directory file protocol host/domain volume folder/directory file Where is the database lookup when accessing a web page In several implementation,the database lookup is at the host domain level. placed at the“fle”level Every host has its own namespace,managed Impacts all operations,including most popular locally. open()and stat() ◆Excellent example of“federated”namespace Great flexibility but huge performance hit,which Extremely efficient,but some limitations implies more hardware and constant database http://www.ietf.org/rfc/rfc2396.txt tuning18 Data Technologies – CERN School of Computing 2019 Name Server  The name server is “the” database of a managed storage system which contains the catalogue of all data (typically all files)  It is a simple lookup-based, single-key, database application for which several implementation exists  DNS (domain name server) software  LDAP databases  Hash tables / Object databases  Relational Databases  Name server reliability is critical  Name server failure brings down the whole storage system  Name server performance is critical  See next slide … 19 Data Technologies – CERN School of Computing 2019 Criticality of the name server performance  Every meta-data operation requires a database transaction.  It is essential to understand where the “name server” approach is placed ...  The name server lookup time dictates the performance of the whole storage system  The database becomes the bottleneck of the entire storage process: low performances are a symptom of major architectural mismatch  Comment: Cloud storage ? An architecture that replaces the name server DB lookup with a “calculated” name resolution (… more to come …) 20 Data Technologies – CERN School of Computing 2019 Short digression on ... Uniform Resource Identifiers (URI)  Example from the web ...  http://csc.cern.ch/data/2012/School/page.htm http://www.ietf.org/rfc/rfc2396.txt protocol host / domain volume folder / directory file  Where is the database lookup when accessing a web page ?  at the host / domain level.  Every host has its own namespace, managed locally.  Excellent example of “federated” namespace  Extremely efficient, but some limitations 21 Data Technologies – CERN School of Computing 2019 Similar problem in storage systems  In several implementation, the database lookup is placed at the “file” level  Impacts all operations, including most popular open() and stat()  Great flexibility but huge performance hit, which implies more hardware and constant database tuning  Example from storage ...  storage://cern.ch/data/2012/School/page.htm protocol host / domain volume folder / directory file