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20031010: CMC grids and a drifting clock at sunysb

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  • Subject: 20031010: CMC grids and a drifting clock at sunysb
  • Date: Fri, 10 Oct 2003 12:10:01 -0600
>From: Brian Colle <address@hidden>
>Organization: SUNY Stony Brook
>Keywords: 200310101646.h9AGkhOb016852 IDD GEM clock

Hi Brian,

I am forwarding along your request for a CMC data feed to Jeff Weber
for attention.

I wanted to touch base with you about the clock drift we see in the
real time statistics plots for thunder.msrc.sunysb.edu.  The latency
plot of the IDS|DDPLUS feed is illustrative of this drift:

http://www.unidata.ucar.edu/cgi-bin/rtstats/iddstats_nc?IDS|DDPLUS+thunder.msrc.sunysb.edu

Since maintenance of an accurate clock is a key factor in the IDD's
ability to deliver real time data with low latencies and no data
losses, we want to strongly encourage you to review the procedure you
are using to set thunder's clock.

We have found that the simplest way for sites to keep an accurate clock
is to run ntpdate at least once per hour from root's cron.  We have
noticed that several sites that are using ntpd have clocks that drift
up to several seconds every 6 hours.  Working with one of those sites
yesterday showed that it is fairly easy to not setup ntpd correctly and
just as easy to correct the problem.  Please let us know if you would
like consultation in getting your clock synced.

Thanks in advance...

Tom Yoksas

>I would like to receive the CMC data feed discussed below via LDM. I am
>developing an ensemble forecast system using MM5 as a part of a COMET
>project (http://fractus.msrc.sunysb.edu/mm5rte/) and we would like to expt
>with CMC grids as initial/bdy data.
>
>my machine:
>thunder.msrc.sunysb.edu
>IP 129.49.65.131
>
>Thank you for your time and consideration.
>
>Brian
>____________________________________________________________
>Dr. Brian Colle         INTERNET: address@hidden
>Assistant Professor
>(631)632-3174
>Institute for Terrestrial and Planetary Atmospheres
>Marine Sciences Research Center
>State University of New York at Stony Brook
>Stony Brook, NY 11794-5000

>From address@hidden Fri Oct 10 13:06:21 2003

Hi Tom,

ntpdate was not cron'd for this machine. I just ran it and it should run
on cron every hour. Things should be better now. Please let me know if you
still see problems.

Brian