xen vm not keeping date/time properly

[Ryan Golhar]

Northrup, Wilson wrote:
> Hello, 
> 
> Have you or are you using the tickless kernel with this setup, and does
> that make a difference?
> 
 > wilson
 >

I don't believe so.  I'm using the standard RHEL 5 installation for bot 
the host and guest, nothing fancy.




> -----Original Message-----
> From: redhat-list-bounces at redhat.com
> [mailto:redhat-list-bounces at redhat.com] On Behalf Of Ryan Golhar
> Sent: Thursday, January 22, 2009 2:45 PM
> To: General Red Hat Linux discussion list
> Subject: Re: xen vm not keeping date/time properly
> 
> 
> 
> George Magklaras wrote:
>>
>> Ryan Golhar wrote:
>>> 9.2.2.2 says xen just passed the time-related calls to Dom0, but that
> 
>>> can't be the case because the times are different.
>>>
>> That is because if you do run ntpd inside the VM, this can create the 
>> problem.
>>
>>> noselect?  inside the VM?
>>>
>> Yes on the guest system, and run ntpd normally on the Dom0.
>>
> 
> I'm running ntpd normally on the host, and ntpd inside the VM using the 
> noselect parameter on the server line, such as:
> 
> server siriusc.umdnj.edu	noselect
> server 0.rhel.pool.ntp.org	noselect
> server 1.rhel.pool.ntp.org	noselect
> server 2.rhel.pool.ntp.org	noselect
> 
> After about a half hour after restarting the ntpd server inside the 
> guest, I'm noticing clock skew of about 30 seconds.  I'm sure this will 
> continue to grow.
> 
> Anyone have any other ideas?
> 
> I'm surprised there isn't a solution to this.  This is a huge problem, 
> especially for an enterprise system that relies on the date/time being 
> correct.
> 
> Ryan
> 
> 
>>> We are running on a Sun SunFire X4150.
>> What I stated was on a Dell 2950 PowerEdge, but I shall get hold of a 
>> SunFire and repeat the test, see if I get the same issue. It does
> state 
>> that there might be some kernel parameters that need tweaking, but, I
> am 
>> curious to find out what's going on, as we will be using SunFire kit 
>> with Xen soon.
>>
>> GM
>>
>>> George Magklaras wrote:
>>>> This page might offer some help:
>>>>
>>>>
>>>> http://support.ntp.org/bin/view/Support/KnownOsIssues#Section_9.2.2.
>>>>
>>>> To recap, we use the 'noselect' keyword to avoid the running ntpd on
> 
>>>> the client to attempt to sync with the defined servers and ntpq does
> 
>>>> not report any disturbing drifts on the client...and we do run ntpd 
>>>> normally (no 'noselect') on Dom0.
>>>>
>>>> What happens (happened if you have already tried) if you try and do 
>>>> this? And what's your hardware platform?
>>>>
>>>> GM
>>>>
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