About performances

[Frank Warmerdam]

Benoit Myard wrote:
> Hi list,
> 
> We are on the process of replacing our custom GIS tools by MapServer
> because it offers greater flexibility and more features. We also
> appreciate its open approach to the GIS universe and the ability to
> integrate it in a wide variety of tools.
> 
> We currently work with E00 data which we convert to Arc/Info Vector
> Coverage (with AVCE00) but we experience major performance issues.
> 
> For a reduced set of data (about 2 MB), MapServer takes up to 15
> seconds to render a rather small map (75,000 km²) on a pretty decent
> hardware (Sun-Fire-T1000 running Solaris 10). Note that MapServer
> doesn't have to reproject the data.
> 
> We wonder if the slowness experienced is due to the data format used;
> if so, which format would you recommend ?

Benoit,

I don't know the details of your data, or what rendering options you
are using.  But if you are rendering polygon layers from arcinfo binary
coverages the polygons have to be assembled from arcs "on the fly" and
this can result in quite a bit of extra seeking around to find data.

I would suggest translating the layer(s) you want to use to shapefiles,
and comparing the performance.  If it is still slow then I think you will
need to provide additional detail or examples of what you are doing that
others can investigate.

> Also, do you think that using the FastCGI approach would significantly
> improve the performances ? I read that FastCGI is good for databases
> but not of much use for files geographic databases; is that still
> true, and what's current status of FastCGI support in MapServer ?

FastCGI helps to make up for high connection costs.  For files that
would equate to formats that are expensive to open.  I doubt very
much that applies in this case.

> Could you share performance reports (data formats used, amount of data
> available, time to render and hardware specs) with the list so that we
> can compare ? Are any of you aware of recent performance benchmarks,
> so that we have a reference ?
> 
> Do you have any ideas or tips to fasten MapServer besides tiles caching ?

1) Use shapefiles
2) Break source data into tiles if you have a very large dataset.
3) spatially index your files.
4) Produce reduced complexity datasets for overview maps that would otherwise
include hundreds of thousands of features.

I think you will find other performance hints in the email archives and
perhaps amoung the web site documentation.  The key is to set it up so
that mapserver only needs to process a reasonable number of features for
a given map request, and that it can find them quickly.

Best regards,
-- 
---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | President OSGeo, http://osgeo.org