The HPCMP provides a long-term storage archive for user files and data backup files at each DSRC. HPCMP mass storage servers use Versity Storage Manager (VSM) to move data files to tape when the files are inactive. VSM is also used to move the files back to disk when a user needs to access the contents of the files. The file status information of the files that are migrated to tape remains on disk, which gives the appearance that the files are still stored on disk.
Mass storage archive servers also use VSM to maintain a nearline storage system, which provides much faster file access than that provided by magnetic tapes. However, the amount of disk space available for nearline storage is dwarfed by the multiple petabytes of space offered by tapes. VSM periodically migrates data files to tape, but retains the directory information about the files on disk. When a user attempts to access the data in a migrated file (e.g., attempting to copy the file), VSM will automatically copy the data file back to disk. Since the access time on the mass storage server can be much longer than the access time on other file systems and file servers, the mass storage server is best suited for long-term and the storage of large files.
For more information about how to access these systems, please refer to the archive guide associated with the specific DSRC you are interested in.