[mapserver-users] Mapserver / Mapcache performance question - file format

[Mark Volz]

Hello,



I am optimize a cache in mapcache that uses mapserver to create images for an air photo service.  I was just wondering if I could get some feedback about optimizing the service.  Here is what I have thus far:



*         All of the images and services are in a single projection

*         The Original four images are in a compresses geotiff file.  (The uncompressed geotiffs are too large)

*         Tileindexes and Overviews were built using gdal at the same resolutions that mapcache will use.

*         A shapefile tile index was created

*         My Mapfile uses PROCESSING "OVERSAMPLE_RATIO =1.0", "GDAL_FORCE_CACHING =YES" and "RESAMPLE=NEAREST"

*         Mapserver is serving tiff files

*         Mapcache is using a 4*4 metatile - I am assuming that this will make about four instances of mapserver run at once, which matches the number of cores I have.  Would it be quicker to use a 16* 16 metatile so that mapserver only needs to open the image once?

*         I am serving the cache in a jpeg, which should keep the cache size small, and the bandwidth down as well.

*         Each tile is 256*256.  I have also seen 512*512 tiles, but I think 256 seems quicker.



I appreciate any thoughts.  Thanks





Mark Volz

GIS Specialist



p.s.  I noticed PROCESSING "OVERSAMPLE_RATIO =1.0" makes a big difference, however I could not find the parameter in any of the official documentation.


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