Re: Time synchronization problem for VMWare with RAC and Linux setup

I am not sure if vmware sync clock really works

I have read that paper since 2006 and never worked in my vmware environments, added kernel parameters, time sync and always ended up with ntp :-/

--
LSC



On 9/3/08, Jeremy Schneider <jeremy.schneider_at_ardentperf.com> wrote:


>

> Thought this thread might be useful to someone, someday.  :)

>

> ---------- Forwarded message ----------

> Subject: Re: Time synchronization problem for VMWare with RAC and Linux

> setup

> To: Eugene Plagge

> Cc: Dan Norris, Ben Prusinski

>

>

> Yeah, IMHO it's best not to involve NTP with VMs.  Time sync is a rather

> complex issue for virtual environments (VMware has had large problems in

> this area).  Here's a great paper on the topic:

> http://www.vmware.com/pdf/vmware_timekeeping.pdf

>

> For your test RAC cluster the VMware clock sync option should work fine -

> we used it for all of the workstations during the lab in Chicago and didn't

> have any problems.  You mentioned that the VM's aren't in sync with each

> other - are they in sync with the server?

>

> On older versions of linux I always used to add the kernel parameter

> "clock=pit" and this helped with clock drift.  You might try that too if

> you're having drift problems.

>

> -Jeremy

>

>

>

>  On Tue, Sep 2, 2008 at 3:38 PM, Eugene Plagge wrote:

>

>

>>   Thanks, Dan,

>>

>> Good tip about using  ntp like that.  We'll  let you know if we discover

>> anything else interesting.

>>

>>

>>

>> Eugene

>>

>>

>>

>>

>>

>> *From:* Dan Norris

>> *Sent:* Tuesday, September 02, 2008 4:23 PM

>> *To:* Eugene Plagge; Jeremy Schneider

>> *Cc:* Ben Prusinski

>> *Subject:* Re: Time synchronization problem for VMWare with RAC and Linux

>> setup

>>

>>

>>

>> Hi Eugene,

>>

>> As Ben pointed out, the VMWare Tools should handle the synchronization. If

>> there's no internet access from the machines, it is possible to set the

>> machines to sync to one another using NTP (as peers) I believe. That way,

>> they may both be off of the "real" time, but they should at least be sync'd

>> with each other and that should allow you to complete the installation.

>>

>> In the worst case, if you set the clocks on each node to be the same

>> within a few seconds, you should be able to complete the installations

>> successfully. In that case, when the nodes reboot, you may have one or the

>> other of them fail to join the cluster if the clocks aren't in sync.

>>

>> Let me know if that doesn't do the trick. Jeremy may also add in his own

>> ideas.

>>

>> Dan

>>

>>

>> On 9/2/08 3:10 PM, "Eugene Plagge" wrote:

>>

>> Hi, Jeremy and Dan,

>> I attended the RAC Attack a few weeks ago.  A colleague and I are having a

>> problem setting up Linux VM machines.

>> The time synchronization does not seem to be working (please see Ben's

>> email below).  I am having similar problems.

>>

>> Any hints or avenues we can try?

>>

>> Thanks very much,

>>

>>

>> ****

>>

>> *From:* Ben Prusinski

>> *Sent:* Tuesday, September 02, 2008 12:30 PM

>> *To:* Doug Hahn

>> *Cc:* Eugene Plagge

>> *Subject:* Time synchronization problem for VMWare with RAC and Linux

>> setup

>>

>>

>> Thanks Doug will do.

>>

>>

>>

>>

>>

>> Hello Gene-

>>

>>

>>

>> I am having problems with my test 2-node RAC setup for Linux on VMWare.

>> The issue is time synchronization for ntp and system clock for both VM

>> machines in the cluster. I installed VMWare tools on both Linux VM guest OS

>> machines to synchronize the time (via the option in the tools menu) but

>> still they are not in sync. This will cause the RAC clusterware installation

>> to fail if both nodes are not in sync with each other. Currently, both test

>> VM machines do not have internet access so I am not able to use the internet

>> NTP servers that are recommended. If you have been able to solve this

>> problem, definitely would appreciate your insight and tips.

>>

>>

>>

>> Thanks in advance,

>>

>> Ben

>>

>>

>> **

>>

>

>

>

> --

> Jeremy Schneider

> Chicago, IL

> http://www.ardentperf.com/category/technical

>

>

>


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