[OpenLayers-Users] Performance vs number of layer

[Julien-Samuel Lacroix]

Hi all,

Since we talk about performance on the dev list...
The more layer we add on the top of an openlayer application, the more 
the application slow down. One of my client's application has around 30 
ka-Map layers available. Let just say that if you switch them all to ON 
at the same time the application becomes a bit...irresponsive.

How much layer did other experience with? How much is too much?

I know performance really depends on the user computer so let's assume 
1CPU (Intel Pentium M 1.73 GHz if you want details), 1GB of RAM and 
Windows XP

With this application we can go up to 8-9 layers at the same time, it's 
slow, but after that it's just too slooooow.

As a solution for this specific case, I think of switching to MapServer 
layer for some of them. Then I could merge the layers displayed in the 
layer switcher as a single MapServer layer and make only one request. 
Would a functionality to merge Mapserver layer request to the same 
server would be a good idea?

Something like the following that would display 3 layers in the layer 
switcher but would be treated as a single one in when querying for a tile.
layer = new OpenLayers.Layer.MapServer( "OpenLayers WMS",
    "http://labs.metacarta.com/wms/vmap0",
    {layers: ['basic', 'road', 'city']},
    {gutter: 15});

Julien


-- 
Julien-Samuel Lacroix
Mapgears
http://www.mapgears.com/