FreeBSD not stable enough for Xen environments?
Jeremy Chadwick
koitsu at FreeBSD.org
Mon Nov 17 12:08:50 PST 2008
On Mon, Nov 17, 2008 at 03:01:02PM -0500, N.J. Thomas wrote:
> * 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
What time counter source does this box have available? The following
will list what's being used (hardware) and what's available (choice):
sysctl kern.timecounter.choice
sysctl kern.timecounter.hardware
Other ideas:
Look into the "fudge" operator of ntp.conf.
Try deleting your ntp driftfile. Note that if you do this, it will take
a day or two for things to "level out". It tries to figure out the
"average" skew rate your system clock has.
> > 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.
Then there's a very good possibility it's hardware-related. At my
workplace, we've had two separate machines in the past couple months
had clocks which "went crazy" -- ntpd reporting 4-5 seconds of skew
every 25-30 minutes. In both cases, the problem turned out to be
broken/bad hardware (crystal or TSC gone bad).
Just something to keep in mind. :-)
--
| Jeremy Chadwick jdc at parodius.com |
| Parodius Networking http://www.parodius.com/ |
| UNIX Systems Administrator Mountain View, CA, USA |
| Making life hard for others since 1977. PGP: 4BD6C0CB |
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