Version management and recoverability for large object data

Abstract

Most applications that access large data objects do so through file systems, but file systems provide an incomplete solution, as they maintain insufficient metadata and do not provide general purpose query engine. Storing large objects in a database addresses these problems, but, for applications that need to update object data, databases are inefficient as they do not provide direct access to data. Additionally, databases often relax the integrity and consistency constraints for large objects, as it the case with objects stored through the Binary Large Object (BLOB) data type. These shortcomings are exacerbated by multiple users or applications that wish to access large objects concurrently. We describe an architecture, based on the Datalink data type, in which large objects in a database are continuously available for read access and can be read and written through a file system interface. Additionally this system does not relax version management, consistency and recoverability guarantees, as with the BLOB data type.