sar: System statistics

Written by Benjamin Cane on 2011-08-12 20:30:06 | 1 min read

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 is a Systems Architect working in the financial services industry focused on platforms that require Continuous Availability. He has been working with Linux and Unix for over 10 years now and has recently published his first book; Red Hat Enterprise Linux Troubleshooting Guide.

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