Terrain Creation: Runtime or static?

Hello Guys,

I've read some articles about using and editing the terrain data and allready created a pretty basic map editor that stores that data in a database. Now I'm a little unsure whether it is better to use a level with a standard terrain and apply the loaded data to that allready existing terrain, or creating a new dynamic terrain in the script and initializing it with the data. Using an exisiting terrain may boost the performance (I can't test that without some detailed levels, so I'd like to ask you), but I may ecnounter artifcials at some point. Maybe through heavy load on the databse and wrong data, etc. What do you guys think is the best approach?

Sencondly: Is there a way to recalculate some of the precompiled effects? Like can I let the author of the map generate the Global Illumination Lightmap at finishing the map? I would like to use some of the effects and apply them uppon loading the map.

And last but not least: How would one hash a file to make a preloading system. I would like to generate a file hash on syncing the map changes, so a client would make hash of the local file, compare it on the server and load the map data only if the local version is different (through corruption, editing, or changes on the server). The entire map file will take about 10-100 mb (deppending on the amount of texture layers, detail layers, etc.), so there isn't that much to calculate.

Thanks for your help in advance and a nice evening, ColdJackle