Strange graph values

[martin]

Hi There everyone
I am trying to monitor our SAN uplinks as we suspect that we have a
bottleneck. I have set up MRTG to monitor the 4 switch ports in
question, but I am seeing some strange results in the max and average
bandwidth fields.
I would expect the max data value to be constant for all the graphs
daily, weekly, monthly yearly. Imstead i have daily=96MB, weekly= 24.6
MB monthly = 11.4MB - this can't be right???
I am trying to use snmpv2c as they are gigabit interfaces - have I set
this up right???

I have turned off scaling for all the graphs except for yearly as we
need to pick up the spikes in bandwidth usage and a sample section
for my config file is below. All the monitored ports are the same
config as the one port shown below

# Created by
# /usr/bin/cfgmaker xxx.xxx.xxx.xxx


### Global Config Options

# for UNIX
# WorkDir: /home/http/mrtg

# for Debian
WorkDir: /var/www/mrtg

# or for NT
# WorkDir: c:\mrtgdata

### Global Defaults

# to get bits instead of bytes and graphs growing to the right
Options[_]: growright, bits

EnableIPv6: no

######################################################################
# System: xxxx
# Description: ProCurve J8693A Switch 3500yl-48G, revision K.13.63,
ROM K.12.17 (/sw/code/build/btm(t3a))
# Contact: Infrastructure_Team
# Location: T0_Equipment_Room
######################################################################


### Interface 41 >> Descr: '41' | Name: '41' | Ip: '' | Eth: '00-17-
a4-89-a2-57' ###

Target[xxxxxx_41]: 41:***@xxx.xxx.xx.xx:::::2
SetEnv[xxxxxxxxx]: MRTG_INT_IP="" MRTG_INT_DESCR="41"
MaxBytes[xxxxxxxxx]: 1250000000
Unscaled[xxxxxxxxxx]: mwd
Title[xxxxxxxxxxxx]: Traffic Analysis for 41 -- sst0b
PageTop[xxxxxxxxxx1]: <h1>Traffic Analysis for 41 (ge/0) -- sst0b</h1>
<div id="sysdetails">
<table>
<tr>
<td>System:</td>
<td>sst0b in
T0_Equipment_Room</td>
</tr>
<tr>
<td>Maintainer:</td>
<td>Infrastructure_Team</td>
</tr>
<tr>
<td>Description:</td>
<td>41 sct0c-ge0 </td>
</tr>
<tr>
<td>ifType:</td>
<td>ethernetCsmacd (6)</td>
</tr>
<tr>
<td>ifName:</td>
<td>41</td>
</tr>
<tr>
<td>Max Speed:</td>
<td>125.0 MBytes/s</td>
</tr>
</table>
</div>

Can someone help explain where I have gone wrong?
Many Thanks

[Andy Davidson]

Post by martin
I would expect the max data value to be constant for all the graphs
daily, weekly, monthly yearly. Imstead i have daily=96MB, weekly= 24.6
MB monthly = 11.4MB - this can't be right???

This is due to the way that data gets averaged automatically. During a
5 min window, the max would have been 96, when this is averaged to a
figure approximating an 'hourly' average say for the monthly view it is
lower.

You could use RRD files as a back end for storing your interface stats
and instruct those (using rrdtool) not to average in the same way.

Thanks
Andy