i've been having problems getting ntp(d) to behave in a Xen DomU.  for
reference, my OP @ the Dovecot list, is

 "[Dovecot] "Time just moved backwards" in Dovecot in a Xen DomU"
 http://www.dovecot.org/list/dovecot/2009-October/043301.html

last comments in that thread suggest that i'm still not properly setup
-- and referred me here.

atm, i've got DomU syncing via NTP, and DomU syncing to Dom) clock --
no ntp. i.e,

@ Dom0
        uname -a
                Linux server 2.6.27.29-0.1-xen #1 SMP 2009-08-15 17:53:59 +0200
x86_64 x86_64 x86_64 GNU/Linux
        cat /proc/sys/xen/independent_wallclock
                1
        cat /sys/devices/system/clocksource/clocksource0/current_clocksource
                jiffies

&, @ DomU
        uname -a
                Linux mx 2.6.27.29-0.1-xen #1 SMP 2009-08-15 17:53:59 +0200 
x86_64
x86_64 x86_64 GNU/Linux
        cat /proc/sys/xen/independent_wallclock
                0
        /sys/devices/system/clocksource/clocksource0/current_clocksource
                xen

i've setup an simple /etc/ntp.conf with discrete Stratum 2 servers
identified -- as pool was giving me headaches with jitters all over
the map.  atm,


        cat /etc/ntp.conf
                restrict default nomodify notrap noquery
                restrict 127.0.0.1
                restrict 192.168.1.0 mask 255.255.255.0  notrust nomodify notrap
                server 192.83.249.28 iburst
                server ac-ntp0.net.cmu.edu iburst
                server ac-ntp1.net.cmu.edu iburst
                server ac-ntp2.net.cmu.edu iburst
                server clock.sjc.he.net  iburst
                driftfile /var/lib/ntp/drift/ntp.drift
                logfile   /var/log/ntpd/ntp.log
                statsdir  /var/log/ntpd/ # directory for statistics files
                filegen   peerstats  file peerstats  type day enable
                filegen   loopstats  file loopstats  type day enable
                filegen   clockstats file clockstats type day enable

with that .conf, checking Dom0's sync,

        ntpq -p -c rv
                assID=0 status=06f4 leap_none, sync_ntp, 15 events, 
event_peer/strat_chg,
                version="ntpd [email protected] Fri May  8 08:40:54 UTC 2009 
(1)",
                processor="x86_64", system="Linux/2.6.27.29-0.1-xen", leap=00,
                stratum=3, precision=-8, rootdelay=83.335, 
rootdispersion=159.494,
                peer=61705, refid=216.218.254.202,
                reftime=ce768a8a.4703f8d6  Tue, Oct  6 2009 20:33:30.277, 
poll=6,
                clock=ce768b42.069eb2c0  Tue, Oct  6 2009 20:36:34.025, state=2,
                offset=-90.860, frequency=-41.421, jitter=253.980, noise=32.331,
                stability=0.073, tai=0
                         remote           refid      st t when poll reach   
delay   offset  jitter
                
==============================================================================
                 zorro.sf-bay.or 216.218.254.202  2 u   21   64    7   18.735  
-459.93 242.982
                +AC-NTP0.net.cmu 128.237.148.140  2 u   23   64    7   84.037  
-448.59 236.990
                +AC-NTP1.net.cmu 128.237.148.140  2 u    7   64   17   79.262  
-487.16 359.409
                +AC-NTP2.net.cmu 128.237.148.132  2 u   48   64    7   84.072  
-396.88 248.950
                *clock.sjc.he.ne .CDMA.           1 u   28   64    7   24.415  
-440.29 252.288

it appears that i _am_ sync'ing, but the jitters seem rather large.

before re-introducing ntp to the DomU -- should those jitters be that
high?  and, if not, what to do about it?

thanks!
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