Hub/Switch Installation Guide

Chapter 1 HPSS Basics
30 September 2002 HPSS Installation Guide
Release 4.5, Revision 2
purge, and storage servers must now exist within a storage subsystem. Each storage subsystem
may contain zerooronegatekeepers to perform site specific user level schedulingof HPSSstorage
requests or account validation. Multiple storage subsystems may share a gatekeeper. All other
serverscontinuetoexistoutsideofstorage subsystems.Siteswhichdonotneedmultiple nameand
bitfile servers are served by running an HPSS with a single storage subsystem.
Storagesubsystemsareassignedintegeridsstartingwithone.Zeroisnotavalidstoragesubsystem
idasserverswhich areindependentof storagesubsystems areassignedto storagesubsystem zero.
Storage subsystem ids must be unique. They do not need to be sequential and need not start with
one,buttheydoso bydefaultunlesstheadministrator specifiesotherwise.Eachstoragesubsystem
has a user-configurable name as well as a unique id. The name and id may be modified by the
administrator at the time the subsystem is configured but may not be changed afterward. In most
cases,the storagesubsystemis referredto byitsname, butinat leastonecase (suffixesonmetadata
file names) the storage subsystem is identified by its id. Storage subsystem names must be unique.
Thereare twotypes of configuration metadata used tosupport storage subsystems: a singleglobal
configuration record, and one storage subsystem configuration record per storagesubsystem. The
global configuration record contains a collection of those configuration metadata fields which are
used bymultiple servers and thatarecommonly modified. The storagesubsystem records contain
configuration metadata which is commonly used within a storage subsystem.
Itispossible to usemultipleSFS servers withina singleHPSS system.Multiplestorage subsystems
areable to runfroma single SFSserver or using one SFSserver per storage subsystem. Inpractice,
differentmetadata filesmaybelocated ondifferentSFS serverson aperfilebasis dependingon the
SFS path given for each file. For configuration and recovery purposes, however, it is desirable for
allofthemetadatafilesforasinglesubsystemtoresideonasingleSFSserver.ThissingleSFSserver
mayeitherbeasingleserverwhichsupportstheentireHPSSsystem,oritmaysupportoneormore
subsystems. Those metadata files which belong to the servers which reside within storage
subsystems are considered to belong to the storage subsystem as well. In an HPSS system with
multiple storage subsystems, there are multiple copies of these files, and the name of each copy is
suffixed with the integer id of the subsystem so that it may be uniquely identified (for example
bfmigrrec.1, bfmigrrec.2, etc.).
Metadata files that belong to a subsystem (i.e. files with numeric suffix) should never be shared
between servers. For example, the Bitfile Server in Subsystem #1 has a metadata file called
bfmigrrec.1.Thisfileshould only beused by theBFS inSubsystem#1,never byanyother server.
The definitions of classes of service, hierarchies, and storage classes apply to the entire HPSS
system and are independent of storage subsystems. All classes of service, hierarchies, and storage
classes areknownto all storage subsystems within HPSS.The levelof resources dedicated to these
entities by each storage subsystem may differ. It is possible to disable selected classes of service
within given storage subsystems. Although the class of service definitions are global, if a class of
service is disabled within a storage subsystem then the bitfile server in that storage subsystem
never selects thatclass of service. Ifa class of serviceisenabled for astorage subsystem, then there
mustbeanon-zerolevelofstorageresourcessupportingthatclassofserviceassignedtothestorage
servers in that subsystem.
Data stored within HPSS is assigned to different Storage Subsystems based on pathname
resolution.A pathname consistingof“/” resolvestothe rootNameServer. TherootName Serveris
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,thepathname“/JunctionToSubsys2” couldlead to therootfileset managed bytheName
Server in Storage Subsystem 2. Sites which do not wish to partition their HPSS through the use of