Hub/Switch Installation Guide

Chapter 7 HPSS User Interface Configuration
HPSS Installation Guide September 2002 461
Release 4.5, Revision 2
LastAccessTimeBeforePurge specifies the number of seconds that must elapse after a file is
accessed before the file becomes eligible for purging.
PurgeDelayTime is the time, in seconds, that the purge process waits between passes in which it
looks for files to purge. If this time is set to zero, HDM waits an infinite amount of time, meaning
the purge process waits for a signal before looking for files to purge. hdm_admin can be used to
send the signal.
UpperBoundandLowerBound areintegersbetween0to100,representingpercentages.Thepurge
process initiates a purge cycle when the percentage of space used on the aggregate exceeds
UpperBound andstopsthecyclewhenthe percentage dropsbelow LowerBound.Needless tosay,
LowerBound should be less than UpperBound.
The choice of values for policy parameters is site specific. Some sites may choose to have an
administrator to determine when to initiate migration and purge cycles. In this case, the infinite
waitpoliciesmentioned abovewouldbe appropriate.Othersitesmaychoosetohavethe migration
and purge cycles to run automatically, and for those sites, the run policies, also described above,
would be better. Inthe secondMigratePolicy in the above example, the migration process is set to
run once every 24 hours, which may work well for a lightly loaded site. For other sites, it may be
necessarytorunthemigrationprocessmorefrequentlytokeepupwiththeload.Thepurgeprocess
should be run often enough to ensure that free space on the system is available. In the example
above, UpperBound andLowerBound were chosento keep between 60% and 80%of DFS on-line.
Using too low of a value for LowerBound could lead to thrashing. Using too high of a value for
UpperBound could cause end users to wait whenever the system needs to free space.
7.6.3.3.5 security.dat File (DFS Systems Only)
The security configuration file, security.dat, is a text file used by the DFS Security Server
componentofHDMforcrosscell accessthroughHPSSinterfacesonmirroredfilesets.The filemust
be located in the same directory as config.dat, typically, /var/hpss/hdm/hdm<id>.
The format of this file is similar to config.dat. Like, config.dat, the first line in security.dat contains
the keyword ServerID,starting incolumn one, and provides its value.The linesfor the remaining
parameters immediately follow and must begin with a TAB character. All of the parameters must
be defined. Following is an extract from a sample security.dat file:
######################################################
# security.dat: sample security configuration file
ServerID 1
ServerName /.:/hpss/hdm
Principal hpss_hdm
KeyTabFile /krb5/hpss.keytabs
RecoveryFile /var/hpss/hdm/hdm1/pag.dat
ObjectID 7622b5a2-226e-11d2-9cdd-08005a4726ef
######################################################
ServerID is anarbitrarynumberusedtodistinguish differentHDM serversdefined inthe security
configuration file. Once ServerID has beenestablished, itshould notbe changed because it is used
during event recovery whenever HDM is restarted. Both config.dat and security.dat must contain
a sectionfor each ServerID that is defined.(Recall that this is one ofthe parameters entered on the
hdm_admin execute line.)