As I understand it, running NTP on a VM is a complete waste of resources, as there is no real per-VM clock to keep in sync. (i.e., you're updating ether) VMWare "fakes" a clock whenever a process tries to access one.
I know there are some kernel boot parameters that can be added to improve time accuracy inside a VM. Not sure if I found them on Redhat's site or VMWare's... That and VMWare tools time synchronization is the best I've been able to come up with. Tim Neu Tel +1 651 756 6383 Fax +1 651 490 4310 Mobile +1 651 238 8816 t...@sjm.com -----Original Message----- From: Kevin Keane [mailto:subscript...@kkeane.com] Sent: Friday, February 27, 2009 3:25 AM Cc: Nagios-users@lists.sourceforge.net Subject: Re: [Nagios-users] Service linked to hostgroup / notifications This isn't really a Nagios issue any more - but here is my experience with this issue: I used to have the same problem with VMWare Server 1.x. Haven't seen it happen in version 2.x, so upgrading might be a good idea if there is no reason for you not to do it. In 1.x, the problem of clock desynchronization really was quite dramatic. The real problem was that the clock drifts so fast that it exceeds ntp's threshold for how much it will adjust. IOW, ntp just plain can't keep up with the extreme clock drift by VMWare. My workaround: create a cron job that as much as every ten minutes restarted the ntp daemon. On restart, ntp will synchronize the time regardless of what the differential is. Of course, the ten minute interval would sometimes be substantially different from actual ten minutes, but that doesn't really matter much here. During these ten minutes, the clock may still drift quite a bit, but at least it will get corrected fairly quickly. David Fontaine wrote: > NTP is configured for every server, except for some virtual machines > synchronizing their clocks with the host on which they are running. > > It happened once or twice that the clock got desynchronized, even > using NTP so I just want to make sure everything is in sync by > monitoring the servers with nagios. > > On Thu, Feb 26, 2009 at 7:48 PM, Lee Azzarello <l...@dropio.com > <mailto:l...@dropio.com>> wrote: > > On Thu, Feb 26, 2009 at 1:17 PM, David Fontaine > <dav.fonta...@gmail.com <mailto:dav.fonta...@gmail.com>> wrote: > > Hello, > > > > I am monitoring a few dozen of servers and I'm really satisfied > with nagios. > > This is a great tool. > > > > However, there's one (actually more than one) thing that I can't > figure out > > : > > > > I define a service : > > > > define service{ > > use generic-service > > hostgroup_name linux-servers > > service_description Time > > check_command check_time!public > > } > > > > This service applies to a host group so that I don't have to > define the > > service for each server. The command doesn't matter but for > completeness > > here's what it does : it compares the time on a remote server > (snmp) to the > > local time and report the difference. > > Going out on a limb here...have you considered using the Network Time > Protocol to keep all your host's clocks in sync with an Internet scale > network of federated time servers available to you for free? > > I'm using NTP on a network of 40 hosts and I never have worried about > their clocks getting out of sync. > > -lee > -- Kevin Keane Owner The NetTech Find the Uncommon: Expert Solutions for a Network You Never Have to Think About Office: 866-642-7116 http://www.4nettech.com This e-mail and attachments, if any, may contain confidential and/or proprietary information. Please be advised that the unauthorized use or disclosure of the information is strictly prohibited. The information herein is intended only for use by the intended recipient(s) named above. 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