IBM HPSS manual Core Server at large

3.7.1. Core Server

The Core Server is responsible for managing the HPSS name space (files, directories, links, etc.), bitfiles, and storage (physical volumes, virtual volumes, etc.) for a single subsystem. Each of these areas of responsibility are outlined in greater detail below.

Core Server at large

The Core Server uses POSIX threads to service concurrent requests. The Core Server accepts requests from any authenticated client; however, certain Core Server functions can be performed only by trusted clients. Trusted clients are those for whom control permission has been set in the Core Server's ACL entry for the client. Higher levels of trust are granted to clients who have both control and write permission set in their ACL entry. Refer to Section 2.1: HPSS Server Security ACLs of the HPSS Management Guide for information concerning the ACL for the Core Server.

The Core Server can be configured to allow or disallow super-user privileges (root access). When the Core Server is configured to allow root access, the UID of the super-user is configurable.

HPSS systems configured with multiple subsystems employ multiple Core Servers and multiple metadata databases. Though the servers are separate, each Core Server in a given HPSS realm must share the fileset global metadata table.

Name Space

The HPSS Core Server maintains the HPSS name space in system metadata. Refer to Section 3.5: HPSS Sizing Considerations on page 68 for details on sizing the name space. Refer to Section 14.8: DB2 Space Shortage of the HPSS Management Guide for information on handling a metadata space shortage. By utilizing multiple storage subsystems, it is possible to distribute large name spaces across multiple Core Servers. Junctions between the names spaces of these storage subsystems can be used to "join" these subsystems.

Bitfiles

The Core Server provides a view of HPSS as a collection of files. It provides access to these files and maps the files onto underlying storage objects.

When a Core Server is configured, it is assigned a server ID. This value should never be changed because it is embedded in the ID of each bitfile and storage segments it uses. HPSS expects to be able to extract the Server ID from any bitfile ID and connect to that server to access the file.

The Core Server maps bitfiles to their underlying physical storage by maintaining information that maps a bitfile to the storage segments that contain its data. For additional information, see Section 3.7.1: Core Server on page 81. The relationship of bitfiles to storage segments and other structures is shown in Figure 9: The Relationship of Various Server Data Structures.

HPSS Installation Guide	July 2008
Release 6.2 (Revision 2.0)	81