HP-UX vPars and Integrity VM V6.3 Administrator Guide

you are certain that the source and target vswitches are connected to the same subnet. Otherwise,
your guest will lose network connectivity after migrating.
For online migration, in addition to sharing the same LAN segment for normal guest connectivity,
the VSPs must be connected with a private 1 GbE (or faster) network for efficient VSP-to-VSP
communications and for secure guest memory transfer. HP strongly recommends using NTP for
time synchronization on all VSPs and guests to maintain consistent time accuracy.
12.3.1 Using Network Time Protocol (NTP) with HP-UX Virtualization
HP recommends using NTP with HP-UX Virtualization to keep time-of-day clocks in sync and correct.
You can use the xntpd command on HP-UX to synchronize time.
NTP configuration on a VSP
On each VSP, NTP must be configured as it would be on any typical (non-virtual) system. In /etc/
ntp.conf file, specify a drift file and one or more high quality time servers:
driftfile /etc/ntp.drift
server <A-HIGH-QUALITY-TIME-SERVER> prefer # a preferred time source
server <ANOTHER-HIGH-QUALITY-TIME-SERVER> # a backup time source
server <YET-ANOTHER-HIGH-QUALITY-TIME-SERVER>
The local clock must also be configured as a fall back if necessary:
server 127.127.1.0 # use local clock as backup
fudge 127.127.1.0 stratum 10 # show poor quality
If you have a group of VSPs that you would like to synchronize, you can add "peer" references in
the /etc/ntp.conf file for each of those associated VSPs, so there is mutual synchronization:
peer <AN-ASSOCIATED-VM-HOST>
peer <ANOTHER-ASSOCIATED-VM-HOST>
peer <YET-ANOTHER-ASSOCIATED-VM-HOST>
After configuring the /etc/ntp.conf file of the VSP, assuming the NTP is already enabled, (that
is, the XNTPD variable in /etc/rc.config.d/netdaemons is set to 1, as in export XNTPD-1),
you can run the /sbin/init.d/xntpd start command to restart the xntpd command on the
HP-UX VSP.
NTP configuration on a vPar and Integrity VM guests
NTP was not designed to run in a virtualized environment. Consequently, you must be careful in
using NTP within vPar and Integrity VM guests. Using the default NTP configuration on guests might
result in NTP instability and failure to synchronize or in apparent lost time within the guest. To
avoid these virtualization related NTP issues, all guests must get time directly from the VSP. Further,
guests must not serve time to any other systems.
You can monitor NTP status by using the ntpq -p command and noting the offset and disp
values. Both values will be under 100. For information about how to check NTP stability, see the
HP-UX Internet Services Administrators Guide.
You can improve time stability within guests by tuning NTP to poll more frequently for time
corrections. The default NTP values for the minpoll and maxpoll intervals are 6 (64 seconds)
and 10 (1024 seconds) respectively. NTP adjusts the current polling interval depending on network
quality and delays. A VM guest uses a virtual LAN that can cause NTP to set the polling value
incorrectly. To mitigate this issue, use the minpoll and maxpoll directives in the ntp.conf file
to change the polling intervals.
Start with minpoll at 4 (16 seconds) and maxpoll at 6 (64 seconds) and then reduce maxpoll
towards 4 if necessary to force shorter polling intervals. HP recommends that guests are never
allowed to deliver time. For this reason, the local clock (server 127.127.1.0) or an ntp.drift
file must not be configured on guests. The ntp.conf file for guests may be as simple as the single
line:
server <VM-HOST-SERVER-NAME> minpoll 4 maxpoll 6
206 Migrating VMs and vPars