Comments on System Monitoring With sar And ksar
System Monitoring With sar And ksar sar is one of the old and famous commandline utilities, which is often overlooked. It provides a wealth of information when you have kind of performance bottlenecks. By itself it only provides lengthy columns of numerical data, kind of hard to interpret. sar exists on most Linux distributions, for example Ubuntu, Debian, CentOS, Gentoo, and is also available on Solaris, AIX, and other commercial Unices. ksar, on the other hand, is a Java based front end for sar's numerical data. It produces friendly graphs which could be exported to .pdf and some other formats.
3 Comment(s)
Comments
Thx. This appears to be one of the simplest historical monitoring system I have seen so far. I like simple. Keep it simple.
Sam
In the crontab entry, you should not be limiting the interval to 1 second. Sar uses the same system resources no matter how long the interval is. It reads kernel values, sleeps, reads the values again and records/prints the difference value. 1 second, 10 seconds, 1200 seconds are the same as far as sar’s resource usage. 99.99% of sar’s usage is sleep, which is what the kernel does anyway when it’s not doing anything. Note below that the first sar sample of only a second showed an average cpu of 3%. The longer samples, averaging over a longer period, show that 6% is probably more of an accurate average, at this time. The web pages I’ve seen so far feed each other with this 1 second sample thing, almost like someone is afraid sar might bog the system down. It won’t. The same two sets of kernel reads happens no matter what the interval is:<br><br>
time sar 1 1; time sar 10 1; time sar 100 1<br>
Linux 2.6.18-194.el5 (blahblah) 10/07/14<br>
12:04:51 CPU %user %nice %system %iowait %steal %idle<br>
12:04:52 all 3.00 0.00 0.75 0.00 0.00 96.25<br>
Average: all 3.00 0.00 0.75 0.00 0.00 96.25<br>
sar 1 1 0.00s user 0.00s system 0% cpu 1.005 total<br>
Linux 2.6.18-194.el5 (blahblah) 10/07/14<br>
12:04:52 CPU %user %nice %system %iowait %steal %idle<br>
12:05:02 all 6.21 0.00 0.93 0.20 0.00 92.67<br>
Average: all 6.21 0.00 0.93 0.20 0.00 92.67<br>
sar 10 1 0.00s user 0.00s system 0% cpu 10.005 total<br>
Linux 2.6.18-194.el5 (blahblah) 10/07/14<br>
12:05:02 CPU %user %nice %system %iowait %steal %idle<br>
12:06:42 all 6.32 0.00 0.97 0.24 0.00 92.47<br>
Average: all 6.32 0.00 0.97 0.24 0.00 92.47<br>
sar 100 1 0.00s user 0.00s system 0% cpu 1:40.01 total<br><br>
From the man page example it shows each hour having 3 20 minute samples. This provides accurate averaging and small sa## files. A 1 second interval each 10 minutes is 1/600th of the information available.<br>
EXAMPLES<br>
To create a daily record of sar activities, place the following entry
in your root or adm crontab file:<br>
0 8-18 * * 1-5 /usr/lib/sa/sa1 1200 3 &<br>
Can you run this command sar remotely? using SSH for example? How?