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I'm serving some large GeoTIFs using GeoServer. I added internal tilling and overviews. With gdaladdo I have two options:

  1. Adding overviews inside the GeoTIF or;
  2. Saving the overviews in an external file (.ovr), using the read only flag (-ro).

gdalinfo recognizes the external ovr file.

Does geoserver recognizes the external overviews in the .ovr file, or should I insert the overviews in the TIF?

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GeoServer before version 2.8 could not see the external overviews but now they should be supported (http://osgeo-org.1560.x6.nabble.com/External-Overviews-for-Geotiff-Support-td5232955.html). Try and test if external overviews are found.

If GeoServer sees external .ovr files and it is using them as fast as internal ones then selecting internal vs. external overviews is a matter of taste. It takes a bit less disk space to build internal overviews. On the other hand, you can simply delete the external ovr. files if you move your images into long term archive. External overviews are also handy for testing different resampling options of gdaladdo. Technically using external overviews is straight forward and there should not be remarkable difference in speed.

  • I have GeoServer 2.9 (what comes with GeoNode). And I did some tests with a GeoTiff with internal and external overviews. But I did not notice much difference. Maybe it's because I was using a smaller tif (800Mb). I'm preparing a larger tif and hope to do some tests next week – Daniel Dec 1 '17 at 18:55
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I have worked with external and internal to the large extent . External pyramids are little bit slow then internal one's because the data has to be ready from the external file . GDAL has to read .ovr file.

Pros of external overview:-

  1. Less space to store.
  2. Handy and can be deelte anytime if not required.

Cons of external overview:-

  1. Less Speed
  2. takes 15% more size w.r.t. actual data size on hard disk.

Pros of internal overview:-

  1. takes 35% more size w.r.t. actual data size on hard disk.
  2. once created you can remove internal pyramids but space used for internal pyramids will not come back. Ex:- if 300 MB original dataset , we build internal it becomes 415MB , when we remove internal pyramids, size of raster will remains 415MB.
  3. can only be build if data set size don't exceed 4 GB

Cons of internal overview:-

  1. Faster Speed.

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