Aug 20th, 2011
sar - Collect, report, or save system activity information.
sar - Collect, report, or save system activity information.
To have sar read a particular data file, use the -f /var/log/sa/saDD option. You can select multiple files by using multiple -f options. Since many of sar’s reports are lengthy, you may want to pipe the output to a file.
To create a basic report showing CPU usage and I/O wait time percentage, use sar with no flags. It produces a report similar to this:
01:10:00 PM CPU %user %nice %system %iowait %idle
01:20:00 PM all 7.78 0.00 3.34 20.94 67.94
01:30:00 PM all 0.75 0.00 0.46 1.71 97.08
01:40:00 PM all 0.65 0.00 0.48 1.63 97.23
01:50:00 PM all 0.96 0.00 0.74 2.10 96.19
02:00:00 PM all 0.58 0.00 0.54 1.87 97.01
02:10:00 PM all 0.80 0.00 0.60 1.27 97.33
02:20:01 PM all 0.52 0.00 0.37 1.17 97.94
02:30:00 PM all 0.49 0.00 0.27 1.18 98.06
Average: all 1.85 0.00 0.44 2.56 95.14
“The %user and %system columns simply specify the amount of time the CPU spends in user and system mode. The %iowait and %idle columns are of interest to us when doing performance analysis. The %iowait column specifies the amount of time the CPU spends waiting for I/O requests to complete. The %idle column tells us how much useful work the CPU is doing. A %idle time near zero indicates a CPU bottleneck, while a high %iowait value indicates unsatisfactory disk performance.”
