Gallery Assist (GA) folder structure. The folder structure of GA is easy to understand. It depends on the following cases:

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A global gallery folder (gallery_assist) wich contains all galleries created through GA.
A gallery user folder (called with the User-ID) wich contains the galleries belongin to the respectively user.
The gallery preset folders.

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The module and the module are activated. A little (GAIC). Thumbnails and preview images are no longer produced from GA.
At this point is ImageCache responsible for this task.