Veritas File System 4.1 Administrator's Guide (HP-UX 11i v3, February 2007)

VxFS Performance: Creating, Mounting, and Tuning File Systems
Monitoring Free Space
Chapter 242
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, reduce the interval between fsadm runs. If the degree of
fragmentation is low, increase the interval between fsadm runs.
The “after” result is an indication of how well the reorganizer has performed. The degree of fragmentation
should be close to the characteristics of an unfragmented file system. If not, it may be a good idea to resize
the file system; 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=/usr/spool/fsadm/out.‘/bin/date +’%m%d’‘
for i in /home /home2 /project /db
do
/bin/echo "Reorganizing $i"
/bin/timex fsadm -F vxfs -e -E -s $i
/bin/timex fsadm -F vxfs -s -d -D $i
done > $outfile 2>&1