HP Integrity Virtual Machines Version 4.2 Release Notes

After configuring the Host's /etc/ntp.conf file, 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 execute /sbin/init.d/xntpd start to restart xntpd on the HP-UX VM Host.
NTP Configuration on a VM Guest
Because NTP was not designed to run inside a virtual machine, using NTP on VM guests requires
special configuration to be stable. Using a typical default NTP configuration on a VM guest might
result in NTP instability and failure to synchronize, or in apparent lost time on the guest. To
avoid these virtualization related NTP issues, each VM guest should get its time directly from
the VM Host. Also, VM guests should not serve time to any other systems.
You can monitor NTP status by using the ntpq -p command and noting the offset and the disp
values. Ideally both values will be well under 100. For information about how to check NTP
stability, see the HP-UX Internet Services Administrators Guide.
You can improve time stability on VM 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 help 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 a VM guest never
be allowed to deliver time (allow guests only to be a time consumers). Because a VM guest never
delivers time, you do not need to configure the local clock (server 127.127.1.0) or an ntp.drift
file. So, the ntp.conf file on a VM guest should be as simple as the single line:
server <VM-HOST-SERVER-NAME> minpoll 4 maxpoll 6
After configuring the guest's /etc/ntp.conf file, assuming 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 following commands on an HP-UX guest to sync its time with the VM Host and
restart xntpd:
/sbin/init.d/xntpd stop
/usr/sbin/ntpdate -b <VM-HOST-SERVER-NAME>
/sbin/init.d/xntpd start
NOTE: For VM guests that are on a different subnet than the VM Host, the VM Host may not
be the best source of time if there is another accurate time server available with less network
latency. In the case of different subnets, measure latency from the guest to various time servers
using the ping and traceroute commands to determine which potential time server has the
least network latency. Using the VM Host may be the best solution, but this depends on your
local network topology and the relative network distance to alternate time servers. If using an
alternate (non-VM-Host) time server appears best, it may be helpful for the alternate time server
and the VM Host to use each other for peer mutual time synchronization.
7.2.4 Supported Adapters
Integrity VM supports only those adapters that are of Ethernet or the IEEE 802.3 CSMA/CD
network. Note that AVIO interfaces are supported by a select set of Ethernet host NICs. The
following Ethernet cards are supported with AVIO on HP-UX guests:
• A6794A — Core
• A6825A — Core
• A7109A — Core
• A6847A — Add-in
• AB465A — Combo Add-in
• A9782A — Combo Add-in
7.2 Known Issues and Information 69