Hi Andrea,
Not to butt in on the conversation, but I am curious about
optimization of ImagePyramids: Could you please define --very-- big files.
Are we talking files near the 2GB ceiling for GeoTiff?
Thanks,
Steve
Stephen Mather
Geographic Information Systems (GIS) Manager
(216) 635-3243
svm@anonymised.com
clevelandmetroparks.com
-----Original Message-----
From: Andrea Aime [mailto:andrea.aime@anonymised.com]
Sent: Tuesday, September 06, 2011 2:34 AM
To: Ziegler Stefan
Cc: geoserver-users@lists.sourceforge.net
Subject: Re: [Geoserver-users] ImagePyramid performance with more than
10'000 tiles
On Tue, Sep 6, 2011 at 7:40 AM, Ziegler Stefan <Stefan.Ziegler@anonymised.com>
wrote:
Hi
We are serving some aerial images with the ImagePyramid plugin. Tiling was
done with gdal_retile: 2000x2000px, Geotiff with LZW compression and alpha
channel. Performance is really nice but from time to time it takes 10 or
more seconds to deliver the wms request. This happens only when Geoserver
has to use the 0 level tiles where we have 11'144 tiles. Can the amount of
tiles in one single directory be a issue? CPU load is not increasing during
the request.
Yes, it can be an issue. The pyramid is just a stacked set of mosaics,
so the pyramid just delegates to the
mosaic readers.
Each mosaic is cached in a soft cache, meaning it can be garbage
collected and in need of being reloaded.
On reload the mosaic will take the shapefile index and load it in
memory, which in the case of a large mosaic
migth take time.
Try adding:
Caching=false
in each and every property file of the mosaics, this should make the
mosaic not load the tile index in memory,
but query on disk every time, which should prevent the 10 seconds
delay (it will of course have a toll on each
request, querying on disk is slower than hitting the in memory index).
There is also the issue of having to open all those little files, in
general it's bad practice to slice information
in a ton of tiny files. Pyramid generated with tools like gdal_retile,
using the default settings,
might be useful for tile caches but in general it's much better to
setup the mosaics with (very) large files
and overviews, and keep low both the number of levels and the number of
files.
Cheers
Andrea
--
-------------------------------------------------------
Ing. Andrea Aime
GeoSolutions S.A.S.
Tech lead
Via Poggio alle Viti 1187
55054 Massarosa (LU)
Italy
phone: +39 0584 962313
fax: +39 0584 962313
http://www.geo-solutions.it
http://geo-solutions.blogspot.com/
http://www.youtube.com/user/GeoSolutionsIT
http://www.linkedin.com/in/andreaaime
http://twitter.com/geowolf
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