Click over the Options icon in the Redshift Shelf to open the plugin options panel. These settings are stored in the Redshift folder, so they are global to all the Redshift scenes. In the options panel you can configure the cache folder, the texture cache max size and the GPUs to be used for rendering.
You have also a debug tab options to configure the log verbosity in the Houdini console.
Currently you need to restart Houdini for these settings take effect. The GPUs configuration changes can work without restart Houdini if you have not rendered any image yet.
