[ntp:questions] Re: Windows - Seven Days Later

David J Taylor david-taylor at blueyonder.co.not-this-bit.nor-this-part.uk
Fri Oct 8 07:00:29 UTC 2004

Jerry Baker wrote:
> I have made several postings about how NTP is having a real problem
> remaining stable. I now have a little more than a weeks worth of data
> graphed with MRTG available. Perhaps I am expecting too much from NTP,
> but it looks to me like there is something critically wrong with NTP's
> operation on the Windows platform (SNTP clients with no stepping keep
> better time).
> Take a look at http://jerbaker.dhs.org/ntp/

My own measurements:


suggest that providing no heavy interactive use is made of the machine, 
NTP works fine - e.g. PCs Bacchus and Hermes.  PC Odin (used for progrm 
development) seems OK as well, but PC Stamsund which is used for making 
photo panoramas and general Web browsing also seems to be subject to the 
sorts of problems you are seeing.  There is no logging in an out on any of 
the PCs.

PC Bacchus is the only machine to rely purely on the Internet, and it is 
pointed at seven Internet servers plus the router on the local cable modem 
headend.  It /does/ get affected if I am making either a full bandwidth 
FTP download lasting more than about 1024 seconds (the poll time that all 
of the servers are currently at), or if I am making a full bandwidth 
upload like a very large e-mail.

PC Odin is used internally as a Web server, and is running very large 
programs processing GB of data per day.  It is transferring an average of 
120kBytes/s from PC Hermes (from a 2Mb/s satellite link) so it is doing a 
heck of a lot of network I/O.

Lost interrupts can be a problem.  I have seen things like video players, 
flash animations etc. cause this, and Sun's Java VM is broken which can 
also cause this problem (you can run Sun's JVM with a startup parameter to 
fix the problem).

You comment that even saving text files causes a problem - can I suggest 
you check that your disks are running DMA and not polled I/O?  Perhaps the 
same with your network cards?


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