iRODS Sample Clauses

iRODS. The iRODS technology plays a central role in the Safe Replication service. This section provides an overview of this technology and describes the main components of iRODS used in the Safe Replication service. 3.1.3.1 A global overview of iRODS 3.1.3.2 iRODS zones and federations 3.1.3.3 Integration with mass storage: Mounted collections versus Compound resource A standard iRODS installation creates one storage resource (known as a Vault), but it is also possible to manage multiple resources (e.g., multiple directories where data should be stored or multiple disks/partitions). Such resources are managed entirely by iRODS, and accessing them directly might render the data in iRODS unusable. Such native iRODS resources are perfectly suited for providing storage space for new data ingested into the system. Sometimes, however, iRODS is installed so as to provide access to existing data sets. This can be achieved by using mounted collections. iRODS does not maintain any metadata information for such collections – in particular, it has no information about the subdirectories and files in the collection. When using this option, iRODS works as a "proxy": each time a request is issued for a data object from a mounted collection, the request is simply passed on to the underlying file system. The advantages of this are twofold. Already existing data can be easily and quickly made available via iRODS (without labour-intensive and time-consuming re-ingests). Secondly, it is possible to modify the content of the mounted collections by using tools other than iRODS without the danger of creating inconsistencies. For a normal collection of data, any low-level direct access and modification (such as the physical removal of a file on the resource) would lead to an inconsistency: iRODS would keep the record describing the data object in the iCAT database, although the object would not be present anymore. The major disadvantage of mounted collections is the fact that metadata functionality is not available. As explained previously, data objects in iRODS are stored on storage resources. Each native iRODS storage resource (that is, the resources that are not mounted collections) must have a unique name, a type and a resource class. The resource can be located on any iRODS server within a given zone (unambiguously identified by the hostname and path). Currently the list of available resource types comprises of the following:  Unix file system,  HPSS file system,  Windows file s...