William Unruh wrote:
On 2017-05-16, David Woolley <david@ex.djwhome.demon.invalid> wrote:
On 16/05/17 16:37, Greg Moeller wrote:
Has anyone come across the advisability of running an
enterprise-wide NTP server under an AIX LPAR? We're currently
running NTP on old Intel hardware and the company policy is to
refresh hardware on a regular basis. It seems a waste to buy
several new servers if we could just put the NTP service on an
AIX LPAR.
If you are talking virtual machines, ntpd should always be run on
the host. Any use on a guest should only be as a leaf node.
Remember also that you could put the ntp server onto some old or
small hardware (eg a Raspberry Pi connected to a GPS with a PPS
output). These is not necessity to run it on large fast expensive
hardware. Also you want to run it on something whose workload does
not fluctuate since work requires energy which produces heat, and the
biggest enemy of accurate clocks is fluctuating temperature of the
clock crystal. The actual value of the temperature does not really
matter, but the fluctuations do.
But as David says, you should never try to run an ntp server on a
virtual machine. Far too much bad interaction between the virtual OS
and the actual hardware, which is what ntp is trying to control.
Of course it depends on the accuracy you want. If +-1sec is good
enough then almost anything you do will work. If you want +- 1
microseconds, you will have to work at it and virtual machines will
be a disaster. If you want 1ns, then you will need special hardware.
3-4 reference servers based on old PC hardware running FreeBSD or maybe
linux can be setup for extremely close to zero cost, add $40-100 for
timing GPS receivers and Bob's your uncle.
Terje
--
- <Terje.Mathisen at tmsw.no>
"almost all programming can be viewed as an exercise in caching"
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