Sysstat package, for me, is a must on any Linux machine I get to deal with. It allows for easy collection of performance data, and it allows easy postmortem of past (short past, anyhow) problems.
For me, the only change from RHEL4 defaults is by setting the time interval to one minute, in stead of the defaults of 10 minutes, as set in /etc/cron.d/sysstat
On RHEL5, however, this process by itself is not enough. RHEL5’s sadc does not collect disk performance information by default. This requires changing the same line, in the same file a bit more. For 64bit systems, the line inside /etc/cron.d/sysstat should look like this:
# run system activity accounting tool every 10 minutes
*/1 * * * * root /usr/lib64/sa/sa1 -d 1 1
# generate a daily summary of process accounting at 23:53
53 23 * * * root /usr/lib64/sa/sa2 -A
The changes from the default are marked in bold.
You need to clean up your past sa files, inside /var/log/sa/ for it to take effect. Wait for few minutes, and you can view disk information by running ‘sar -d‘