FreeBSD not stable enough for Xen environments?

[N.J. Thomas]

* Maxim Khitrov <mkhitrov at gmail.com> [2008-11-17 14:47:00+0000]:
> > I've not seen any problems with the clock on my RootBSD Xen system.
> > I do run the ntpd in base and on average, my clock is usually only
> > about 15ms away from "true UTC".
> 
> That's interesting. Can you post your `ntpq -p` output here?

Sure:

    $ ntpq -p
         remote           refid      st t when poll reach   delay   offset  jitter
    ==============================================================================
    +clock.trit.net  192.12.19.20     2 u  529 1024  377   81.554    2.870   6.477
    +mail.honeycomb. 192.43.244.18    2 u  408 1024  377   44.091   10.986   8.250
    *tuppy.intrepidh 64.142.103.194   2 u  413 1024  377   67.709   15.626  10.327
    +clock3.redhat.c 66.187.233.4     2 u  445 1024  377  147.283   24.455   9.397
    +204.34.198.40   .USNO.           1 u  409 1024  377   88.746   20.620  10.405
    +tick.usno.navy. .USNO.           1 u  427 1024  377   20.848   18.916   8.212
    +ntp-s1.cise.ufl .GPS.            1 u  421 1024  377   45.709   18.067   9.222
     LOCAL(0)        LOCAL(0)        10 l   18   64  377    0.000    0.000   0.004

This is what I pretty much used to eyeball my offset earlier.

> When ntpd is running, its polling interval stays very low (around 64
> seconds) because it keeps having to reset the clock. My message log is
> filled with the following:

Intersting, I see the same in my logs, but the frequency seems to be
much less than yours, e.g. for the month of November:

    Nov  1 00:08:22 zaph ntpd[678]: time reset -0.129649 s
    Nov  3 15:33:09 zaph ntpd[678]: time reset -0.137509 s
    Nov  4 03:11:51 zaph ntpd[678]: time reset +0.237734 s
    Nov  4 03:34:23 zaph ntpd[678]: time reset -0.150326 s
    Nov  4 13:05:20 zaph ntpd[678]: time reset +0.317738 s
    Nov  4 13:32:06 zaph ntpd[678]: time reset -0.560629 s
    Nov  4 13:54:35 zaph ntpd[678]: time reset +0.265391 s
    Nov  4 15:43:55 zaph ntpd[678]: time reset -0.163660 s
    Nov  7 17:31:03 zaph ntpd[678]: time reset -0.130039 s
    Nov 10 18:29:19 zaph ntpd[678]: time reset +0.169785 s
    Nov 10 19:46:26 zaph ntpd[678]: time reset -0.146554 s
    Nov 10 20:27:08 zaph ntpd[678]: time reset +0.891811 s
    Nov 10 20:53:59 zaph ntpd[678]: time reset -0.774636 s
    Nov 10 21:35:45 zaph ntpd[678]: time reset +0.384227 s
    Nov 10 22:33:46 zaph ntpd[678]: time reset -0.194131 s
    Nov 11 12:34:25 zaph ntpd[678]: time reset +0.433002 s
    Nov 11 13:01:09 zaph ntpd[678]: time reset -0.335592 s
    Nov 11 15:17:45 zaph ntpd[678]: time reset +0.933537 s
    Nov 11 16:01:42 zaph ntpd[678]: time reset -0.510371 s
    Nov 11 17:29:41 zaph ntpd[678]: time reset -0.133244 s
    Nov 11 19:16:41 zaph ntpd[678]: time reset +0.191431 s
    Nov 11 19:42:30 zaph ntpd[678]: time reset -0.458738 s
    Nov 11 20:09:16 zaph ntpd[678]: time reset +0.207999 s
    Nov 11 20:36:06 zaph ntpd[678]: time reset +0.143897 s
    Nov 14 01:29:44 zaph ntpd[678]: time reset +0.134492 s
    Nov 15 13:13:36 zaph ntpd[678]: time reset +0.199937 s
    Nov 15 14:45:09 zaph ntpd[678]: time reset -0.205131 s

> And so on... Could it be a problem with the hardware on host machine?
> I use the same ntp.conf file on several FreeBSD 7.1 servers, and the
> VPS is the only one that has this problem.

I checked on my other FreeBSD boxes (all 7.0) and none of them (VPS or
otherwise) exihibit this problem.

> I upgraded my VPS to 7.1 a few months ago, but I don't remember if I
> had this problem when using 7.

Mine is a 7.0.

Thomas