Re: iowait

From: Jeff (cech_at_minn.net)
Date: 08/28/03 

Date: 27 Aug 2003 20:25:28 -0700

Syn <syn_NOSPAM_uw@hotmail.com> wrote in message news:<3F4C6EC7.90706@hotmail.com>...
> Jerry Jorgenson wrote:
>
> > Set sar to run at 10 minute intervals (in adm's crontab).
> >
> > run sar -w # Shows no swapping if the four columns are zero
>
>
> First thanks to all of you who replied me, now I wanted to run sar but
> when I run sar I get the following error message:
>
> sar: Can't open /var/adm/sa/sa27
>
> Do I need to enable something or so ?
>
> Regards

First, run 'chkconfig | grep sar' to confirm that sar is turned on.
If it isn't you can start it by running 'chkconfig sar on' (as root)
and the next time you reboot it will start by default.

By default, sar polls the system once every 20 minutes between 8am and
5pm, I think, and once per hour outside those times and saves the data
in /var/adm/sa/sa## where the numbers correspond to the day of the
month for that date.

When you run sar from the command line with no options, you are
actually using sar to display the most basic data from the present
day. If you want to display a different days data use the -f option
to point it to a different file.

If 20 minutes isn't often enough for your purposes, you can either
change the settings on sar's cron entry, or you can simply run sar
from the command line, specifying an output file, a time interval (in
seconds) and a number of times to run it (in iterations). The syntax
would look like 'sar -o sar.out 1 60' to run it every seconds 60
times.

Then, once the data is collected you can use the sar -f sar.out -{any
of several options} to see various things.

Running sar with the -o option from the command line will work
regardless of the chkconfig flag, so if sar is not turned on by
default you can still collect and analyse performance information.

Read man sar for more.

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