Search results for "Metadata repository"
showing 4 items of 4 documents
One Phase Commit: A Low Overhead Atomic Commitment Protocol for Scalable Metadata Services
2012
As the number of client machines in high end computing clusters increases, the file system cannot keep up with the resulting volume of requests, using a centralized metadata server. This problem will be even more prominent with the advent of the exascale computing age. In this context, the centralized metadata server represents a bottleneck for the scaling of the file system performance as well as a single point of failure. To overcome this problem, file systems are evolving from centralized metadata services to distributed metadata services. The metadata distribution raises a number of additional problems that must be taken into account. In this paper we will focus on the problem of managi…
Metadata to Support Data Warehouse Evolution
2009
The focus of this chapter is metadata necessary to support data warehouse evolution. We present the data warehouse framework that is able to track evolution process and adapt data warehouse schemata and data extraction, transformation, and loading (ETL) processes. We discuss the significant part of the framework, the metadata repository that stores information about the data warehouse, logical and physical schemata and their versions. We propose the physical implementation of multiversion data warehouse in a relational DBMS. For each modification of a data warehouse schema, we outline the changes that need to be made to the repository metadata and in the database.
Contextual Metadata for Document Databases
2005
Metadata has always been an important means to support accessibility of information in document collections. Metadata can be, for example, bibliographic data manually created for each document at the time of document storage. The indexes created by Web search engines serve as metadata about the content of Web documents. In the semantic Web solutions, ontologies are used to store semantic metadata (Berners-Lee et al., 2001). Attaching a common ontology to a set of heterogeneous document databases may be used to support data integration. Creation of the common ontology requires profound understanding of the concepts used in the databases. It is a demanding task, especially in cases where the …
Direct lookup and hash-based metadata placement for local file systems
2013
New challenges to file systems' metadata performance are imposed by the continuously growing number of files existing in file systems. The total amount of metadata can become too big to be cached, potentially leading to multiple storage device accesses for a single metadata lookup operation. This paper takes a look at the limitations of traditional file system designs and discusses an alternative metadata handling approach, using hash-based concepts already established for metadata and data placement in distributed storage systems. Furthermore, a POSIX compliant prototype implementation based on these concepts is introduced and benchmarked. A variety of file system metadata and data operati…