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Chapter 1 HPSS Basics
HPSS Installation Guide September 2002 21
Release 4.5, Revision 2
added, new classes of service can be set up. HPSS files reside in a particular class of service which
users select based on parameters such as file size and performance. A class of service is
implemented by a storage hierarchy which in turn consists of multiple storage classes, as shown in
Figure 1-2. Storage classes are used to logically group storage media to provide storage for HPSS
files. A hierarchy may be as simple as a single tape, or it may consist of two or more levels of disk,
disk array, and local tape. The user can even set up classes of service so that data from an older type
of tape is subsequently migrated to a new type of tape. Such a procedure allows migration to new
media over time without having to copy all the old media at once.
1.2.7 Storage Subsystems
To increase the scalability of HPSS in handling concurrent requests, the concept of Storage
Subsystem has been introduced. Each Storage Subsystem contains a single Name Server and Bitfile
Server. If migration and purge are needed for the storage subsystem, then the Storage Subsystem
will also contain a Migration / Purge Server. A Storage Subsystem must also contain a single Tape
Storage Server and/or a single Disk Storage Server. All other servers exist outside of Storage
Subsystems. Data stored within HPSS is assigned to different Storage Subsystems based on
pathname resolution. A pathname consisting of / resolves to the root Name Server. The root Name
Server is the Name Server specified in the Global Configuration file. However, if the pathname
contains junction components, it may resolve to a Name Server in a different Storage Subsystem.
For example, the pathname /JunctionToSubsys2 could lead to the root fileset managed by the
Name Server in Storage Subsystem 2. Sites which do not wish to partition their HPSS through the
use of Storage Subsystems will effectively be running an HPSS with a single Storage Subsystem.
Note that sites are not required to use multiple Storage Subsystems.
1.2.8 Federated Name Space
Federated Name Space supports data access between multiple, separate HPSS systems. With this
capability, a user may access files in all or portions of a separate HPSS system using any of the
configured HPSS interfaces. To create a Federated Name Space, junctions are created to point to
filesets in a different HPSS system. For security purposes, access to foreign filesets is not supported
for NFS, or for end-users of FTP and the Non-DCE Gateway when only the local password file is
used for authentication.
1.3 HPSS Components
The components of HPSS include files, filesets, junctions, virtual volumes, physical volumes,
storage segments, metadata, servers, infrastructure, user interfaces, a management interface, and
policies. Storage and file metadata are represented by data structures that describe the attributes
and characteristics of storagesystem components such as files, filesets, junctions, storage segments,
and volumes. Servers are the processes that control the logic of the system and control movement
of the data. The HPSS infrastructure provides the services that are used by all the servers for
standard operations such as sending messages and providing reliable transaction management.
User interfaces provide several different views of HPSS to applications with different needs. The
management interface provides a way to administer and control the storage system and implement
site policy.
These HPSS components are discussed below in Sections 1.3.1 through 1.3.7.