Using Sar To Monitor System Performance
The sar utility, which is part of the systat package, can be used to review history performance data on your server. System resource utilization can be seen for given time frames to help troubleshoot performance issues, or to optimize performance.
Sysstat can be easilly installed using the yum package manager:
yum install sysstat
The installation includes a cron task, located at /etc/cron.d/sysstat, which collects system performance information every ten minutes. This polling interval can be changed simply by modifying the cron task.
After some time for the cron task to begin collecting data, the sar command can be used to display collected information. Executing the command without arguments will provide system load information on the current day.
The -s (for start) and -e (for end) flags can be used to narrow the displayed information to a specific timeframe.
# sar -s 02:30:00 -e 04:00:00
For previous days, you’ll need to specify the -f flag, along with a path to that days stat file; which are located under /var/log/sa/. To see data for the 9th, you would use the sa09 file.
# sar -f /var/log/sa/sai09
Live information can be collected and displayed by specifying the interval of collection, and the number of times to collect; sar interval run_times seconds, 10 times, run:
sar 5 10
Additional flags can be passed to sar to display other collected data.
FLAG EXAMPLE Memory: -r sar -r Disk: -d sar -d Processor: -P sar -P 0 -P 1 sar -P ALL Network: -n sar -n DEV