Chapter 2 HPSS Planning
62 September 2002 HPSS Installation Guide
Release 4.5, Revision 2

2.5.8 XFS

XFS for Linux is an open source filesystem from SGI based on SGI’s XFS filesystem for IRIX.
HPSShas the capability to backend XFS and transparently archive inactive data. This frees XFS disk
tohandle data that is being actively utilized, giving users the impression of an infinitely large XFS
filesystem that performs at near-native XFS speeds.
It is well suited to sites with large numbers of small files or clients who wish to use NFS to access
HPSS data. However, the files can only be accessed through XFS (or NFS via XFS) interfaces and
cannotbe accessed with HPSS utilities such as parallel FTP. Therefore,data transfer performance is
limited to XFS speeds.
2.6 HPSS Server Considerations
Servers are the internal components of HPSS. They must be configured correctly to ensure that
HPSS operates properly. This sections describes key concepts and notions of the various servers
and their impact on system use, operation, and performance.

2.6.1 Name Server

The HPSS Name Server (NS) maintains a data base in five Encina SFS files. An SFS relative
sequencedfile is used to store data associated with NS objects. (NS objects are bitfiles, directories,
symbolic links, junctions and hard links.) The four other files are SFS clustered files. Two of these
filesstore text data and ACL entries, and the remaining two files are SFS clustered files that are used
to store fileset information.
The total number of objects permitted in the name space is limited by the number of SFS records
allocatedto the NS. Refer to Section 2.10.2.4 for details on selecting the size of the name space. With
thisrelease of HPSS, provisions have been made for increasing the size of the name space by adding
additional Name Servers, storage subsystems, or by junctioning to a Name Server in a different
HPSSsystem (see Section 11.2.3: Federated Name Space on page 279 of the HPSS Management Guide).
Refer to Section 10.7.3: Name Server Space Shortage (page 272) in theHPSS Management Guide for
information on handling an NS space shortage.
TheNS uses DCE threads to service concurrent requests. Refer to Section 6.5.1: Configure the Basic
Server Information (page 263) for more information on selecting an appropriate number of DCE
threads. The NS accepts requests from any client that is authenticated through DCE; however,
certainNS functions can be performed only if the request is from a trusted client. Trustedclients are
thoseclients for whom control permission has been set in their CDS ACL entry for the NS. Higher
levels of trust are granted to clients who have both control and write permission set in their CDS
ACL entry. Refer to Table 6-3:Basic Server Configuration Variables on page 266 for information
concerning the CDS ACL for the Name Server.
TheNS can be configured to allow or disallow super-user privileges (root access). When the NS is
configured to allow root access, the UID of the super-user is configurable.
Multiple Name Servers are supported, and each storage subsystem contains exactly one Name
Server.Though the servers are separate, each Name Server in a given DCE cell must share the same
metadata global file for filesets.