[time-nuts] Timing performance of servers

lists at lazygranch.com lists at lazygranch.com
Thu Oct 25 01:38:31 EDT 2012


Just a FYI here, using Dave's logging program, I found large errors in NTP when the antivirus did its thing. I don't know if it was due to CPU activity interfering with NTP or the cabinet heating up when the antivirus was running.
  
-----Original Message-----
From: "David J Taylor" <david-taylor at blueyonder.co.uk>
Sender: time-nuts-bounces at febo.com
Date: Thu, 25 Oct 2012 06:03:44 
To: Time-Nuts<time-nuts at febo.com>
Reply-To: Discussion of precise time and frequency measurement
	<time-nuts at febo.com>
Subject: Re: [time-nuts] Timing performance of servers

Fellow time-nuts,

When spending time on a conference last week, I heard one interesting
comment that they lost data due to bad timing on their Windows servers.
[]
If you need better performance than that, you should use NTP (and then
download and install Meinbergs Windows-client for NTP).

Then again, I would point out that for this type of data, it would most
probably be better served on a Linux box.

What should be a nice wake-up call for them would be a summation of how
different strategies would give them clock precision of sufficient
grade. So, does anyone know of such measurements presented anywhere?
[]
Cheers,
Magnus
====================================================

Magnus,

If it helps, I have my own measurements of the Meinberg NTP port and later 
versions running on Windows here:

  http://www.satsignal.eu/mrtg/performance_ntp.php

Strategy:
1  - have one FreeBSD (not Linux) server, although this is now not 
essential, but it's nice as a confirmation that the rest is working OK.

2 - Configure some Windows PCs as stratum-1 servers fed from GPS.  On the 
plots above, PCs Alta, Bacchus, Feenix and Stamsund are acting as stratum-1 
servers.  These all have serial port connections, and cover the OS range 
Windows 2000, XP, Win-7/32 and Win-7/64.  All are using the kernel-mode 
serial port driver patch developed by Dave Hart.  PC Pixie is the FreeBSD 
box.

3 - For the client PCs, use a fixed 32-second polling interval to the local 
stratum-1 servers, with Internet servers as a backup polled at 1024 seconds, 
resulting in a configuration file something like:

_______________________________________________
# Use drift file
driftfile "C:\Tools\NTP\etc\ntp.drift"

# Use specific local NTP servers
server 192.168.0.3    iburst    minpoll 5 maxpoll 5 prefer    # Pixie
server 192.168.0.2    iburst    minpoll 5 maxpoll 5        # Feenix
server 192.168.0.7    iburst    minpoll 5 maxpoll 5        # Stamsund

# Use pool NTP servers
pool uk.pool.ntp.org    iburst    minpoll 10
_______________________________________________


The client performance varies, with some of the best results being on a 
Windows-8 Wi-Fi connected PC which seems to have very good drivers (PC 
Bergen).  Jitter is 40 - 110 microseconds.  Windows XP also shows low 
jitter, but greater offset (within 250 microseconds).

Windows Vista was the worst performer I had, but that PC has now been 
retired.  There are discussions in progress at the moment about improving 
Windows-Vista and Windows-7 as a Windows time interval setting and reporting 
bug has been discovered, particularly affecting NTP.

Cheers,
David
-- 
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor at blueyonder.co.uk 


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