[thredds] joinExisting and FMRC aggregation performance

• To: THREDDS community <thredds@xxxxxxxxxxxxxxxx>
• Subject: [thredds] joinExisting and FMRC aggregation performance
• From: "Signell, Richard" <rsignell@xxxxxxxx>
• Date: Fri, 13 Mar 2015 16:50:35 -0400

Thredds community,

The largest archive of HF Radar ocean surface current data is being
served by THREDDS at
http://hfrnet.ucsd.edu/thredds/catalog.html, but the erratic
performance of the joinExisting aggregations has made them difficult
to use.  The folks at UCSD discovered that if they use FMRC
aggregations they work much better than the joinExisting, as borne out
by this Ipython Notebook, where we just request WMS services from the
two aggregations every minute for one hour:

http://nbviewer.ipython.org/gist/rsignell-usgs/139d5481d74a1181e576

I don't understand this behavior.  The joinExisting was designed for
this type of aggregation (simply joining netcdf files along the time
dimension) and the FMRC was instead designed for files with
overlapping forecast times.  But there is no arguing with the results
of this test: FMRC is clearly working better.

Anyone have insight into why we are getting these results?

Are there settings that could be changed to improve the performance of
the joinExisting aggregation?

Thanks,
Rich

P.S. the existing aggregation catalog and threddsConfig.xml settings
are shown at the end of the notebook

-- 
Dr. Richard P. Signell   (508) 457-2229
USGS, 384 Woods Hole Rd.
Woods Hole, MA 02543-1598

• Follow-Ups:
  • Re: [thredds] joinExisting and FMRC aggregation performance
    • From: John Caron