Figure 2. Class of Service / Hierarchy / Storage Class
2.3.1. HPSS Files, Filese ts, Volumes, Storage Seg ments and Related Metadata
The various metadata constructs used to describe the HPSS namespace and HPSS storage are
described below:
•Files (Bitfiles). Files in HPSS, called bitfiles in deferen ce to IEEE Mass Storage Reference
Model terminology, are logical strings of bytes, even though a particular bitfile may have a
structure imposed by its owner. This unstructured view decouples HPSS from any particular
file management system that host clients of HPSS might use. HPSS bitfile size is limited to264
- 1 bytes.
Each bitfile is identified by a machine-generated name called a bitfile ID. It may also have a
human readable name. It is the job of the HPSS Core Server (discussed in Section 2.3.2) to
map a human readable name to a bitfile's ID.
•Filesets. A fileset is a logical collection of files that can be managed as a single administrative
unit, or more simply, a disjoint directory tree. A fileset has two identifiers: a human readable
name and a numeric fileset ID. Both identifiers are unique to a given realm.
•Junctions. A junction is a Core Server object, much like a symbolic link to a directory, that is
used to point to a fileset. This fileset may belong to the same Core Server or to a di fferent
Core Server. When pointing to a different Core Server, junctions allow HPSS users to traverse
to different subsystems.
•File Families. HPSS files can be grouped into families. All files in a given family are
recorded on a set of tapes assigned to the family. Only files from the given family are
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