sysstat is a package of monitoring tools, which includes iostat, mpstat, pidstat, sar, sadc, sa1, sa2 and sadf
iostat
Reports CPU statistics and input/output statistics for devices, partitions and network filesystems.
mpstat
Reports individual or combined processor related statistics.
pidstat
Reports statistics for Linux tasks (processes) : I/O, CPU, memory, etc.
sar
Collects,
reports and saves system activity information (CPU, memory, disks,
interrupts, network interfaces, TTY, kernel tables,etc.)
sadc
Is the system activity data collector, used as a backend for sar.
sa1
Collects and stores binary data in the system activity daily data file. It is a front end to sadc designed to be run from cron.
sa2
Writes a summarized daily activity report. It is a front end to sar designed to be run from cron.
sadf
Displays
data collected by sar in multiple formats (CSV, XML, etc.) This is
useful to load performance data into a database, or import them in a
spreadsheet to make graphs. To use this tools, you need to install
One great feature of this tools is that you can configure it to run as a daemon, and it will log a lot of info about your system. To start it if you are using Debian, edit with your favorite text editor, in my case is vi vim /etc/default/sysstat
And change the line: ENABLED="false" to ENABLED="true", so that file may look like this
sysstat
apt-get install sysstatOne great feature of this tools is that you can configure it to run as a daemon, and it will log a lot of info about your system. To start it if you are using Debian, edit with your favorite text editor, in my case is vi vim /etc/default/sysstat
And change the line: ENABLED="false" to ENABLED="true", so that file may look like this
# # Default settings for /etc/init.d/sysstat, /etc/cron.d/sysstat # and /etc/cron.daily/sysstat files # # Should sadc collect system activity informations? Valid values # are "true" and "false". Please do not put other values, they # will be overwritten by debconf! ENABLED="true" # Additional options passed to sa1 by /etc/init.d/sysstat # and /etc/cron.d/sysstat # By default contains the `-d' option responsible for # generating disk statisitcs. SA1_OPTIONS="-d" # Additional options passed to sa2 by /etc/cron.daily/sysstat. SA2_OPTIONS=""
sa1 is a variant of sadc, which is designed to work as a cronjob, just like sa2 which is a variant of sar command also designed to be run as cronjob. If you are not using Debian, you will not have the /etc/default/sysstat, so you will have to add to your root's cronjob file this lines:
0 8-18 * * 1-5 /usr/lib/sysstat/sa1 1200 3 & 5 19 * * 1-5 /usr/lib/sysstat/sa2 -A &The -d option in sa1 makes it to store disks data, which by default are not written. Now you can use
sar to see the data stored, in your system, check the page of the project for more information about this performance toolkit
A common task for System Administrators is to monitor and care for a
server. That's fairly easy to do at a moment's notice, but how to keep a
record of this information over time? One way to monitor your server
is to use the Sysstat package.
Sysstat is actually a collection of utilities designed to collect information about the performance of a linux installation, and record them over time.
It's fairly easy to install too, since it is included as a package on many distributions.
To install on Centos 4.3, just type the following:
yum install sysstat
We now have the sysstat scripts installed on the system. Lets try the sar command.
sar
Linux 2.6.16-xen (xen30) 08/17/2006 11:00:02 AM CPU %user %nice %system %iowait %idle 11:10:01 AM all 0.00 0.00 0.00 0.00 99.99 Average: all 0.00 0.00 0.00 0.00 99.99 Several bits of information, such as Linux kernel, hostname, and date are reported.
More importantly, the various ways CPU time being spent on the system is shown.
%user, %nice, %system, %iowait, and %idle describe ways that the CPU may be utilized.
%user and %nice refer to your software programs, such as MySQL or Apache.
%system refers to the kernel’s internal workings.
%iowait is time spent waiting for Input/Output, such as a disk read or write. Finally, since the kernel accounts for 100% of the runnable time it can schedule, any unused time goes into %idle.
The information above is shown for a 1 second interval. How can we keep track of that information over time?
If our system was consistently running heavy in %iowait, we might surmise that a disk was getting overloaded, or going bad.
At least, we would know to investigate.
So how do we track the information over time? We can schedule sar to run at regular intervals, say, every 10 minutes.
We then direct it to send the output to sysstat’s special log files for later reports.
The way to do this is with the Cron daemon.
By creating a file called sysstat in /etc/cron.d, we can tell cron to run sar every day.
Fortunately, the Systat package that yum installed already did this step for us.
more /etc/cron.d/sysstat
# run system activity accounting tool every 10 minutes */10 * * * * root /usr/lib/sa/sa1 1 1 # generate a daily summary of process accounting at 23:53 53 23 * * * root /usr/lib/sa/sa2 -A The sa1 script logs sar output into sysstat’s binary log file format, and sa2 reports it back in human readable format.
The report is written to a file in /var/log/sa.
ls /var/log/sa
Sysstat is actually a collection of utilities designed to collect information about the performance of a linux installation, and record them over time.
It's fairly easy to install too, since it is included as a package on many distributions.
To install on Centos 4.3, just type the following:
yum install sysstat
We now have the sysstat scripts installed on the system. Lets try the sar command.
sar
Linux 2.6.16-xen (xen30) 08/17/2006 11:00:02 AM CPU %user %nice %system %iowait %idle 11:10:01 AM all 0.00 0.00 0.00 0.00 99.99 Average: all 0.00 0.00 0.00 0.00 99.99 Several bits of information, such as Linux kernel, hostname, and date are reported.
More importantly, the various ways CPU time being spent on the system is shown.
%user, %nice, %system, %iowait, and %idle describe ways that the CPU may be utilized.
%user and %nice refer to your software programs, such as MySQL or Apache.
%system refers to the kernel’s internal workings.
%iowait is time spent waiting for Input/Output, such as a disk read or write. Finally, since the kernel accounts for 100% of the runnable time it can schedule, any unused time goes into %idle.
The information above is shown for a 1 second interval. How can we keep track of that information over time?
If our system was consistently running heavy in %iowait, we might surmise that a disk was getting overloaded, or going bad.
At least, we would know to investigate.
So how do we track the information over time? We can schedule sar to run at regular intervals, say, every 10 minutes.
We then direct it to send the output to sysstat’s special log files for later reports.
The way to do this is with the Cron daemon.
By creating a file called sysstat in /etc/cron.d, we can tell cron to run sar every day.
Fortunately, the Systat package that yum installed already did this step for us.
more /etc/cron.d/sysstat
# run system activity accounting tool every 10 minutes */10 * * * * root /usr/lib/sa/sa1 1 1 # generate a daily summary of process accounting at 23:53 53 23 * * * root /usr/lib/sa/sa2 -A The sa1 script logs sar output into sysstat’s binary log file format, and sa2 reports it back in human readable format.
The report is written to a file in /var/log/sa.
ls /var/log/sa
sa17 sar17
sa17 is the binary sysstat log, sar17 is the report. (Today date is the 17th)
There is quite alot of information contained in the sar report, but there are a few values that can tell us how busy the server is.
Values to watch are swap usage, disk IO wait, and the run queue.
These can be obtained by running sar manually, which will report on those values.
sar
How about my swap usage, am I running out of Ram? Being swapped out is normal for the Linux kernel, which will swap from time to time. Constant swapping is bad, and generally means you need more Ram.
sar -W
How about system load? Are my processes waiting too long to run on the CPU?
sar -q
Notice that there is a 1, 5, and 15 minute interval on the right.
Having the three time intervals gives you a feel for how much load the system is carrying.
A 3 or 4 in the 1 minute average is ok, but the same number in the 15 minute
column may indicate that work is not clearing out, and that a closer look is warranted.
This was a short look at the Sysstat package.
We only looked at the out put of three of sar attributes, but there are others.
Now, armed with sar in your toolbox, your system administration job just became a little easier.
There is quite alot of information contained in the sar report, but there are a few values that can tell us how busy the server is.
Values to watch are swap usage, disk IO wait, and the run queue.
These can be obtained by running sar manually, which will report on those values.
sar
Linux 2.6.16-xen (xen30) 08/17/2006 11:00:02 AM CPU %user %nice %system %iowait %idle 11:10:01 AM all 0.00 0.00 0.00 0.00 99.99 11:20:01 AM all 0.00 0.00 0.00 0.00 100.00 11:30:02 AM all 0.01 0.26 0.19 1.85 97.68 11:39:20 AM all 0.00 2.41 2.77 0.53 94.28 11:40:01 AM all 1.42 0.00 0.18 3.24 95.15 Average: all 0.03 0.62 0.69 0.64 98.02There were a few moments where of disk activity was high in the %iowait column, but it didnt stay that way for too long. An average of 0.64 is pretty good.
How about my swap usage, am I running out of Ram? Being swapped out is normal for the Linux kernel, which will swap from time to time. Constant swapping is bad, and generally means you need more Ram.
sar -W
Linux 2.6.16-xen (xen30) 08/17/2006 11:00:02 AM pswpin/s pswpout/s 11:10:01 AM 0.00 0.00 11:20:01 AM 0.00 0.00 11:30:02 AM 0.00 0.00 11:39:20 AM 0.00 0.00 11:40:01 AM 0.00 0.00 11:50:01 AM 0.00 0.00 Average: 0.00 0.00Nope, we are looking good. No persistant swapping has taken place.
How about system load? Are my processes waiting too long to run on the CPU?
sar -q
Linux 2.6.16-xen (xen30) 08/17/2006 11:00:02 AM runq-sz plist-sz ldavg-1 ldavg-5 ldavg-15 11:10:01 AM 0 47 0.00 0.00 0.00 11:20:01 AM 0 47 0.00 0.00 0.00 11:30:02 AM 0 47 0.28 0.21 0.08 11:39:20 AM 0 45 0.01 0.24 0.17 11:40:01 AM 0 46 0.07 0.22 0.17 11:50:01 AM 0 46 0.00 0.02 0.07 Average: 0 46 0.06 0.12 0.08No, an average load of .06 is really good.
Notice that there is a 1, 5, and 15 minute interval on the right.
Having the three time intervals gives you a feel for how much load the system is carrying.
A 3 or 4 in the 1 minute average is ok, but the same number in the 15 minute
column may indicate that work is not clearing out, and that a closer look is warranted.
This was a short look at the Sysstat package.
We only looked at the out put of three of sar attributes, but there are others.
Now, armed with sar in your toolbox, your system administration job just became a little easier.
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