HP JFS 3.3 and HP OnLineJFS 3.3 VERITAS File System 3.3 System Administrator's Guide

Chapter 5 103
Performance and Tuning
Monitoring Free Space
length
• more than 5 percent of the total file system size available as free
extents in lengths of 64 or more blocks
A badly fragmented file system will have one or more of the following
characteristics:
• greater than 5 percent of free space in extents of less than 8 blocks in
length
• more than 50 percent of free space in extents of less than 64 blocks in
length
• less than 5 percent of the total file system size available as free
extents in lengths of 64 or more blocks
The optimal period for scheduling of extent reorganization runs can be
determined by choosing a reasonable interval, scheduling fsadm runs at
the initial interval, and running the extent fragmentation report feature
of fsadm before and after the reorganization.
The “before” result is the degree of fragmentation prior to the
reorganization. If the degree of fragmentation is approaching the figures
for bad fragmentation, then the interval between fsadm runs should be
reduced. If the degree of fragmentation is low, the interval between
fsadm runs can be increased.
The “after” result is an indication of how well the reorganizer is
performing. The degree of fragmentation should be close to the
characteristics of an unfragmented file system. The file system may be a
candidate for expansion. (Full file systems tend to fragment and are
difficult to defragment.) It is also possible that the reorganization is not
being performed at a time during which the file system in question is
relatively idle.
Directory reorganization is not nearly as critical as extent
reorganization, but regular directory reorganization will improve
performance. It is advisable to schedule directory reorganization for file
systems when the extent reorganization is scheduled. The following is a
sample script that is run periodically at 3:00 A.M. from cron for a
number of file systems:
outfile=/tmp/fsadm_out.&212#;/bin/date +’%m%d’&212#;
for i in /home /home2 /project /db
do