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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>You have to be very careful about
virtualising an MRTG server because of clock skew.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If the MRTG server is calculating any
rates (IE, if it have a Target which is NOT type ‘gauge’) then it
is liable to clock skew. This is when the virtual system clock lags
behind and jumps forward erratically due to the virtualisation scheduling of
the server. You do not normally notice this because the lag is when the
virtual server is inactive; however it can cause inaccuracies when calculating
rates of change, particularly if the virtual container is heavily loaded (high guest
‘ready time’ in VMware), or if the polling interval is short.
It will result in the graphs becoming more ‘spiky’ then in reality.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>In addition, if you are monitoring CPU or
Memory usage of a virtual machine via MRTG, then the values you get will be
completely misleading. The only way to get real values is from the
virtual container itself – eg, with VMware, from the VirtualCentre
API. I have a MRTG plugin for VMWare to achieve this.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Finally, a heavily-loaded MRTG server will
have high disk IO, making it a bad candidate for virtualisation as this affects
performance.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I’d really recommend you don’t
virtualise a MRTG server, but if you have to, then make sure the ready time is
very low, you use 5min polling, and don’t use MRTG ‘native mode’.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>If you’re planning on attending
LISA09, I’m going to try and give a talk on ‘Virtualisation and
MRTG’ via Skype at the MRTG BoF session.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Steve<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<div style='border:none;border-left:solid blue 1.5pt;padding:0cm 0cm 0cm 4.0pt'>
<div>
<div class=MsoNormal align=center style='text-align:center'><font size=3
face="Times New Roman"><span lang=EN-US style='font-size:12.0pt;font-family:
"Times New Roman"'>
<hr size=2 width="100%" align=center tabindex=-1>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
mrtg-bounces@lists.oetiker.ch [mailto:mrtg-bounces@lists.oetiker.ch] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Ramika Lawson<br>
<b><span style='font-weight:bold'>Sent:</span></b> Thursday, 1 October 2009
11:20 a.m.<br>
<b><span style='font-weight:bold'>To:</span></b> mrtg@lists.oetiker.ch<br>
<b><span style='font-weight:bold'>Subject:</span></b> [mrtg] mrtg in vmware</span></font><font
size=3 face="Times New Roman"><span lang=EN-US style='font-size:12.0pt;
font-family:"Times New Roman"'><o:p></o:p></span></font></p>
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<p class=MsoNormal><font size=2 face=Calibri><span style='font-size:11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span lang=EN-US style='font-size:
11.0pt'>Hi Steve, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span lang=EN-US style='font-size:
11.0pt'>How can MRTG be virtualized? <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span lang=EN-US style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span lang=EN-US style='font-size:
11.0pt'>Regards, <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span lang=EN-US style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=5 color="#632423"
face="Edwardian Script ITC"><span lang=EN-US style='font-size:18.0pt;
font-family:"Edwardian Script ITC";color:#632423'>Ramika Lawson<o:p></o:p></span></font></p>
<p class=MsoNormal style='text-autospace:none'><font size=2 color="#632423"
face="Trebuchet MS"><span lang=EN-US style='font-size:10.0pt;font-family:"Trebuchet MS";
color:#632423'>Senior Network Engineer - ITS <o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 face=Calibri><span lang=EN-US style='font-size:
11.0pt'><o:p> </o:p></span></font></p>
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