Veritas File System 5.0 Administrator's Guide (September 2006)
■ 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 improves 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
Tuning I/O
The performance of a file system can be enhanced by a suitable choice of I/O sizes
and proper alignment of the I/O requests based on the requirements of the
underlying special device. VxFS provides tools to tune the file systems.
45VxFS performance: creating, mounting, and tuning file systems
Tuning I/O