[thredds] Advantages of using FMRC over JoinExisting

• To: <thredds@xxxxxxxxxxxxxxxx>
• Subject: [thredds] Advantages of using FMRC over JoinExisting
• From: "Signell, Richard" <rsignell@xxxxxxxx>
• Date: Tue, 4 Dec 2012 18:22:23 -0500

Thredds folks,

We've got 33 years of ocean model output  in monthly NetCDF3 files
that we have been aggregating into a single virtual 33TB dataset using
joinExisting aggregation along the time dimension:
http://www.smast.umassd.edu:8080/thredds/hindcasts.html?dataset=fvcom/hindcasts/30yr_gom3

This works fine, but two issues have arisen:

1) the monthly files start at 0000 on the first day of the month, and
end on 2400 of the last day of the month.  Thus when aggregated with
joinExisting, we get duplicate time and data values at the end of
every month.

2) when accessing the data via OPeNDAP, the dataset doesn't have an
unlimited time dimension.   This causes the "nc3tonc4" conversion
program in NetCDF4-Python to try to read each variable in it's
entirety, which of course is problematic.  If "nc3tonc4" sees an
unlimited dimension, it can "chunk" its way along.

So we could eliminate both these problems by using a FMRC aggregation, right?

Thanks,
Rich

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

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  • Re: [thredds] Advantages of using FMRC over JoinExisting
    • From: Signell, Richard