•Class of Service (COS). Each bitfile has an attribute called Class Of Service. The COS
defines a set of parameters associated with operational and performance charact eristics of a
bitfile. The COS results in the bitfile being stored in a storage hierar chy suitable for its
anticipated and actual size and usage characteristics. Figure 2: Class of
Service/Hierarchy/Storage Class shows the relationship between COS, storage hierarchies,
and storage classes.
2.3.2. HPSS Servers
HPSS servers include the Core Server, Migration/Purge Server, Gatekeeper, Location Server, Log
Client, Log Daemon, Physical Volume Library, Physical Volume Repository, Mover, Storage System
Manager, and, possibly, a Data Migration Gateway. Figure 3: HPSS Components provides a
simplified view of the HPSS system. Each major server component is shown, along with the basic
control communications paths (thin arrowed lines). Infrastructure items (those components that “glue
together” the distributed servers) are shown at the top of the cube. These infrastructure items are
discussed in Section 2.3.4: HPSS Infrastructure on page 44. HPSS user interfaces (the clients listed
in the figure) are also discussed in Section 2.3.5: HPSS User Interfaces on page 47.
Figure 3. HPSS Components
•Core Server. The Core Server provides several key sets of functionality.
First, the Core Server provides translation between human-oriented names and HPSS object
identifiers. Name space objects managed by the Core Server are filesets, junctions, directories,
files, hard links, and symbolic links. The Core Server provides access verification to obje cts
and mechanisms for manipulating access to these objects via a Portable Operating System
Interface (POSIX) view of the name space. This name space is a hierarchical structure
HPSS Installation Guide July 2008
Release 6.2 (Revision 2.0) 40