-Jukka tileindex, mapserver, and the gdal wms driver
On Mon, 2014-02-03 at 17:20 +0000, Jukka Rahkonen wrote: > Luke Roth <roth.luke <at> gmail.com> writes: > > > > > Another thing that might speed up access is setting the config > option GDAL_DISABLE_READDIR_ON_OPEN = TRUE, either as an environment > variable or on the command line. That should help with GDAL reading the > directory each time it opens a dataset. I have an application which reads > one value from each of a large number of datasets and setting this option > made it run about 3 times faster. > > > Hi, > > You are right. This config option makes GDAL to skip the reading of the > remote directory and saves a lot of bandwidth: > > VRT case: > Bytes Received: 4 244 509 (of which the vrt file: 4 192 577) > Sequence (clock) duration: 00:00:09.9996000 > Was: > Bytes Received: 6 459 443 > Sequence (clock) duration: 00:00:37.8130000 > > BigTIFF case: > Bytes Received: 2 158 917 > Sequence (clock) duration: 00:00:04.4368000 > Was: > Bytes Received: 4 374 137 > Sequence (clock) duration: 00:00:30.9192000 > > > Conclusion: > Both options are unsuitable for serious use while amusing to play with. > Reading the BigTIFF tile offset index (or whatever it is) seems to mean > about 2 MB of compultory payload traffic. Reading the VRT file means in this > example 4 MB of payload. If this sort of net access to a large directory of > raster files should be important for someone there should be a way to find > the right raster file and righ data range in that file with minimum amount > of bytes. Perhaps some kind of rtree indexed vrt file? First aid might be to > keep the vrt file on the client side. > > -Jukka Rahkonen- > > > _______________________________________________ > gdal-dev mailing list > gdal-dev@lists.osgeo.org > http://lists.osgeo.org/mailman/listinfo/gdal-dev _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev
