[gdal-dev] Raster Strategies Examples

[Edi KARADUMI]

I have read many strategies for raster performance, but i still have
problems with my case. The posts that i have read explain the strategie, but
are not very detailed. Im new to mapserver so i have problems implementing
them. My case is:

-about 6000 tiles that form the map
-170mb each tile
-aproximately 1.2T of iamges
-i have 10T HD and i think disk space is not a problem for me
-tile format is TIF
-tile size 9375x6250 pixels

The strategy i have implemented and the problems i have

-First i divided the tiles in 60 folders, to increase the performance in
disk seek/read.

-Than i transformed source files into internally tiles with the command
   gdal_translate -of GTiff -co "TILED=YES" original.tif tiled.tif

-i used gdaladdo to add internal pyramids

   gdaladdo -r average 2 4 8 16 32 64 128

-Created a tileindex using
   gdaltindex -write_absolute_path MapAll.shp
//server/Maps/Subfolder1/*.tif

-Created a spatial index .qix file
   shptree MapAll.shp

-than added the layer to the mapfile without the .shp extension so the
application can use the .qix

as you may know, i have very slow performance when i zoom out and im stucked
here. As i have read i should make a copy of the tiles with reduced
resolution. Merge the tiles together and use min/max scale to show different
layers in different scales. the min/max scales i zoom in/out are
100/1200000. Now my questions are

- How can i calculate the scale where i should create another layer of the
tiles, or i shoud see it with some tests?

- how much should be the resolution of the new layer?

- is there any tools or program to merge the tiles? merging 6000 tiles with
the gdalwarp by writing the command by myself is frustrating

- how many tiles should i merge together to create the new layer? (how many
tiles should have the new layer) i know that in each zoomscale its better to
appear only one tile but i dont know how to calculate it

- the tiles that i should merge are the originals or those with internal
tiling and overviews?
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