IBM Hub/Switch 7.6.2 Filesets, 7.6.2.1 Archived Filesets - (DFS or XFS), 7.6.2.2 Mirrored Filesets

Chapter 7 HPSS User Interface Conﬁguration

436 September 2002 HPSS Installation Guide

Release 4.5, Revision 2

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.

Astandard 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

managedﬁle system and HPSS. For DFS systems, HPSS supports partially resident ﬁle data in both

DFSand 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

ﬁlesystem 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

DFSsupports 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)

HPSSis 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

managedwith 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

conﬁgurationpolicies. 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)

Consistencybetween 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