Filesets - IBM Hub/Switch Installation Manual

Chapter 7 HPSS User Interface Configuration
of cells to allow data access and authorization between clients and servers in different cells. DFS
uses the Episode physical file system, although it can use other native file systems, such as UFS.
HPSS provides a similar interface through the Linux version of SGI's XFS file system.
A standard interface is used to couple DFS and XFS (the "managed" file systems) with HPSS. The
integrated system provides transparent, automatic archiving and caching of data between the
managed file system and HPSS. For DFS systems, HPSS supports partially resident file data in both
DFS and HPSS and allows changes made to a file or directory through DFS interfaces to be visible
through HPSS interfaces and vice versa. For XFS systems, access is available only via XFS
interfaces, and file data is either wholly resident or wholly absent.
The standard selected to couple DFS and XFS with HPSS is The Open Group's Data Storage
Management standard (XDSM). The API provided for in this standard is called the Data
Management API (DMAPI), and the two acronyms, 'XDSM' and 'DMAPI', are often used
interchangably. The XDSM standard originated in the mid-nineties from the Data Management
Interfaces Group (DMIG). It is a low-level interface to the physical file system which provides the
Data Management application (DMAP) with the ability to store important attribute information
with a file. It also allows for the generation of notifications to the DMAP on occurrence of various
file system operations. XDSM enables the DMAP to control disk storage by allowing the DMAP to
move disk-resident file data to tertiary storage systems and vice-versa.
7.6.2

Filesets

DFS supports logical collections of files called filesets. A fileset is a directory subtree, administered
as a unit, that can be mounted in the global name space. Multiple DFS filesets may reside on an
aggregate, which is analogous to a disk partition. Filesets may be moved between DFS aggregates,
either on the same or different servers to achieve load balancing.
XFS supports the classic filesystem which resides on and fills an assigned disk partition.
For the HPSS/DFS interface, two data management configuration options, archived filesets and
mirrored filesets, are available which differ in the way the fileset is managed by HPSS.
For the HPSS/XFS interface, only the archived configuration option is supported.
7.6.2.1 Archived Filesets - (DFS or XFS)
HPSS is used strictly as an archive facility for the managed filesystem. Access to the name and data
space is provided only through the managed file system's interfaces. Filesets and filesystems
managed with this option are called 'archived filesets'. The files in an archived fileset contain copies
of file data from any managed filesystem files that have migrated to HPSS. Pathnames to these
HPSS files are generated by the HPSS Data Management Application (HDM) based on
configuration policies. HPSS root may access objects in these filesets, but all client access is via the
managed filesystem.
7.6.2.2 Mirrored Filesets - (DFS only)
Consistency between HPSS and DFS name and data spaces is maintained. DFS data is archived to
HPSS. Access to the name and data space is available through both DFS and HPSS interfaces, with
436 September 2002 HPSS Installation Guide
Release 4.5, Revision 2