[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.
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
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?
If it helps, I have my own measurements of the Meinberg NTP port and later
versions running on Windows here:
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
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
# 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.
SatSignal Software - Quality software written to your requirements
Email: david-taylor at blueyonder.co.uk
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