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Old 01-22-2009, 02:52 PM
George Magklaras
 
Default xen vm not keeping date/time properly

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

--
--
George Magklaras BSc Hons MPhil
RHCE:805008309135525

Senior Computer Systems Engineer/UNIX-Linux Systems Administrator
EMBnet Technical Management Board
The Biotechnology Centre of Oslo,
University of Oslo
http://folk.uio.no/georgios




Ryan Golhar wrote:
I've seen a ton of messages like this but no solution that works. I
have a 64-bit RHEL 5 machine running multiple guests. Dom0 keeps time
using ntp and works well.


I initially had the virtual machines do the same thing, but they failed
to keep time properly. I've since disabled ntp on the guests and
haven't found a solution.


I saw messages regarding setting /proc/sys/xen/independent_wallclock to
0, but I only see this file on Dom0, not the guests so I'm not quite
sure how this works for the guests keeping proper time.


Has anyone figured out how to keep 64-bit guests in sync with Dom0?

Ryan



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Old 01-22-2009, 03:30 PM
Ryan Golhar
 
Default xen vm not keeping date/time properly

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.


noselect? inside the VM?

We are running on a Sun SunFire X4150.

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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Old 01-22-2009, 04:49 PM
George Magklaras
 
Default xen vm not keeping date/time properly

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.


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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Old 01-22-2009, 06:44 PM
Ryan Golhar
 
Default 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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Old 01-22-2009, 09:21 PM
"Northrup, Wilson"
 
Default xen vm not keeping date/time properly

Hello,

Have you or are you using the tickless kernel with this setup, and does
that make a difference?

wilson

-----Original Message-----
From: redhat-list-bounces@redhat.com
[mailto:redhat-list-bounces@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
>>>
>
Notice: This e-mail message, together with any attachments, contains
information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station,
New Jersey, USA 08889), and/or its affiliates (which may be known
outside the United States as Merck Frosst, Merck Sharp & Dohme or
MSD and in Japan, as Banyu - direct contact information for affiliates is
available at http://www.merck.com/contact/contacts.html) that may be
confidential, proprietary copyrighted and/or legally privileged. It is
intended solely for the use of the individual or entity named on this
message. If you are not the intended recipient, and have received this
message in error, please notify us immediately by reply e-mail and
then delete it from your system.


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Old 01-23-2009, 05:58 AM
Jose R R
 
Default xen vm not keeping date/time properly

2009/1/22 Ryan Golhar <golharam@umdnj.edu>:
> I've seen a ton of messages like this but no solution that works. I have a
> 64-bit RHEL 5 machine running multiple guests. Dom0 keeps time using ntp
> and works well.
>
> I initially had the virtual machines do the same thing, but they failed to
> keep time properly. I've since disabled ntp on the guests and haven't found
> a solution.

Those organizations that offer Virtual Private Servers (VPS) would not
be in business if they had not found a solution to the problem you
describe As an instance, using such technologies as HyperVM (<
http://lxlabs.com/software/hypervm/ >) they offer their clients *any*
of a variety of Xen DomU GNU/Linux distributions.

You may want to try the following procedure (from an CentOS list):

----------Begin fragment-------------------------------

Put this in /etc/sysctl.conf :

xen.independent_wallclock = 1

and then execute sysctl.

What happens then is that the domU will do it's own timekeeping and no
longer follow the dom0. Now this also means that you need to run a
ntpd inside the domU to make sure it's clock keeps syncronised.
-----------End Fragment---------------------------------
< http://lists.centos.org/pipermail/centos-virt/2008-January/000185.html >

Best regards.

--
Jose R R
http://www.metztli-it.com
--------------------------------------------------------------------------------------------------------------------
IBM Lotus Symphony is officially supported on Red Hat, SuSE, and
Ubuntu GNU/Linux
-------------------------------------------------------------------------------------------------------------------

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Old 01-23-2009, 02:03 PM
Ryan Golhar
 
Default xen vm not keeping date/time properly

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@redhat.com
[mailto:redhat-list-bounces@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


Notice: This e-mail message, together with any attachments, contains
information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station,
New Jersey, USA 08889), and/or its affiliates (which may be known
outside the United States as Merck Frosst, Merck Sharp & Dohme or
MSD and in Japan, as Banyu - direct contact information for affiliates is
available at http://www.merck.com/contact/contacts.html) that may be
confidential, proprietary copyrighted and/or legally privileged. It is
intended solely for the use of the individual or entity named on this
message. If you are not the intended recipient, and have received this
message in error, please notify us immediately by reply e-mail and
then delete it from your system.


--
redhat-list mailing list
unsubscribe mailto:redhat-list-request@redhat.com?subject=unsubscribe
https://www.redhat.com/mailman/listinfo/redhat-list
 
Old 01-23-2009, 02:05 PM
Ryan Golhar
 
Default xen vm not keeping date/time properly

Jose R R wrote:

2009/1/22 Ryan Golhar <golharam@umdnj.edu>:

I've seen a ton of messages like this but no solution that works. I have a
64-bit RHEL 5 machine running multiple guests. Dom0 keeps time using ntp
and works well.

I initially had the virtual machines do the same thing, but they failed to
keep time properly. I've since disabled ntp on the guests and haven't found
a solution.


Those organizations that offer Virtual Private Servers (VPS) would not
be in business if they had not found a solution to the problem you
describe As an instance, using such technologies as HyperVM (<
http://lxlabs.com/software/hypervm/ >) they offer their clients *any*
of a variety of Xen DomU GNU/Linux distributions.

You may want to try the following procedure (from an CentOS list):

----------Begin fragment-------------------------------

Put this in /etc/sysctl.conf :

xen.independent_wallclock = 1

and then execute sysctl.

What happens then is that the domU will do it's own timekeeping and no
longer follow the dom0. Now this also means that you need to run a
ntpd inside the domU to make sure it's clock keeps syncronised.
-----------End Fragment---------------------------------
< http://lists.centos.org/pipermail/centos-virt/2008-January/000185.html >

Best regards.



Yes, I've seen this. There is not indication on whether this setting
should be inside the guest or on the host. MY guess was the guest. I
put this in, restart the guest and it had no effect. I believe (from
google searching) this only applies to paravirtualized machines. Mine
is fully virtualized.


Any other ideas?

Ryan

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