sar: System statistics

Sar is a utility that will grab cpu, disk i/o, memory, and network statistics on a 10 minute interval. Sar is great for grabbing system statistics quickly; I use sar whenever I'm doing any kind of performance tuning or troubleshooting.

To use sar all you need to do is install the sysstat package. The package will install a cron in /etc/cron.d that will kick off a sar capture every 10 minutes. If you want you can change this to every 5 minutes by modifying the crontab.

Sar will even keep a months worth of data in /var/log/sa/saXX where XX represents the day of month.

**Example: **

[[email protected] tmp]# sar  
Linux 2.6.35.13-92.fc14.i686 (bcane.virtuals.local)  08/08/2011  _i686_ (1 CPU)  
  
09:05:01 AM CPU %user %nice %system %iowait %steal %idle  
09:10:01 AM all 0.10 0.00 0.13 0.15 0.00 99.61  
09:15:02 AM all 0.29 6.90 1.59 14.22 0.00 77.01  
09:20:01 AM all 0.02 0.00 0.10 0.14 0.00 99.74  
09:25:01 AM all 0.02 0.00 0.10 0.03 0.00 99.86  
09:30:01 AM all 0.02 0.09 1.13 12.63 0.00 86.12  
09:35:01 AM all 0.02 0.00 0.13 0.46 0.00 99.39  
09:40:01 AM all 0.02 0.00 0.14 0.57 0.00 99.27

To read a specific days file you can specify it with the -f option.

[[email protected] tmp]# sar -f /var/log/sa/sa08  
Linux 2.6.35.13-92.fc14.i686 (bcane.virtuals.local)  08/08/2011  _i686_ (1 CPU)  
  
09:05:01 AM CPU %user %nice %system %iowait %steal %idle  
09:10:01 AM all 0.10 0.00 0.13 0.15 0.00 99.61  
09:15:02 AM all 0.29 6.90 1.59 14.22 0.00 77.01  
09:20:01 AM all 0.02 0.00 0.10 0.14 0.00 99.74  
09:25:01 AM all 0.02 0.00 0.10 0.03 0.00 99.86  
09:30:01 AM all 0.02 0.09 1.13 12.63 0.00 86.12  
09:35:01 AM all 0.02 0.00 0.13 0.46 0.00 99.39  
09:40:01 AM all 0.02 0.00 0.14 0.57 0.00 99.27  
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Benjamin Cane
Principal Engineer, Vice President

Benjamin Cane is Principal Engineer at American Express. He has more than 16 years of experience with roles in both systems and software engineering. He leverages both his systems and software skills to build end-to-end platforms. Platforms, purpose built for performance and resiliency. Benjamin is also the author of Red Hat Enterprise Linux - Troubleshooting Guide (2015, Packt Publishing), and he has published many popular articles on topics such as Linux, Docker, Python, Go and Performance Tuning. Thoughts and Opinions expressed in my articles are my own.

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