<html dir="ltr"><head> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"> <meta content="MSHTML 6.00.6000.16915" name="GENERATOR"> <style title="owaParaStyle"></style> </head> <body ocsi="x"> <div dir="ltr"><font face="Tahoma" color="#000000" size="2">I would be very very wary of running Nagios on a VM (we use VMware here). The reason for this is Clock Skew.</font></div> <div dir="ltr"><font face="tahoma" size="2"></font> </div> <div dir="ltr"><font face="tahoma" size="2">Clock Skew causes the virtual clock on the guest OS to lag behind then skip forward depending on the loading and sleep times of the guest. Note that this will not affect 'Para-virtualised' guests as they share the hardware clock, but these are only possible in some Xen guests at the moment AFAIK and are not common. VMWare can't do them.</font></div> <div dir="ltr"><font face="tahoma" size="2"></font> </div> <div dir="ltr"><font face="tahoma" size="2">On a lightly loaded physical machine your clock skew will be negligible but as load goes up you can get the guest clock lagging as much as 10sec or even more. This can screw up latencies, scheduling, rate calculations (such as CPU use and net use) and so on. In addition any monitoring of virtualised resource (CPU, Memory) will be completely wrong unless you obtain the values from a source which is aware of the virtualiasation (eg VMWare tools API or VirtualCentre API for vmware)</font></div> <div dir="ltr"><font face="tahoma" size="2"></font> </div> <div dir="ltr"><font face="tahoma" size="2">Clock skew and virtualised resource monitoring has caused too many problems in our tests and we now only use physical servers for Nagios (and MRTG).</font></div> <div dir="ltr"><font face="tahoma" size="2"></font> </div> <div dir="ltr"><font face="tahoma" size="2">I have a Nagios plugin check_vmware at <a href="http://www.steveshipway.org/forum">www.steveshipway.org/forum</a> for monitoring VMware virtualised resources via the API to get meaningful values - previous used check_esx3 but this has been superceeded by the use of the VC API in check_vmware</font></div> <div dir="ltr"><font face="tahoma" size="2"></font> </div> <div dir="ltr"><font face="tahoma" size="2">Steve</font></div> <div dir="ltr"><font face="tahoma" size="2"></font> </div> <div id="divRpF34050" style="DIRECTION: ltr"> <hr tabindex="-1"> <font face="Tahoma" size="2"><b>From:</b> Juki [juki.emma@gmail.com]<br> <b>Sent:</b> Friday, 13 November 2009 12:42 a.m.<br> <b>To:</b> Nagios Users Mail-list<br> <b>Subject:</b> [Nagios-users] Installing Nagios Server on a Virtual Machine<br> </font><br> </div> <div></div> <div>Hello people, <div><br> </div> <div>I would like to know if it is advisable (or best practice) to install and run a Nagios monitoring server on a virtual machine (in this case, with OpenSuSE as the OS) with </div> <div>the intention of monitoring physical hardware client machines on the same LAN.</div> <div><br> </div> <div>If so, what known issues should I look out for in this case?</div> <div><br> </div> <div>Thanks,</div> <div>Juki</div> </div> </body> </html>