Mapnik render from a postgres cluster on an external drive

Because of limited space on my laptop I had to set up my europe-latest.osm.pbf on an external drive. Keeping the flat-nodes on my laptop reduces the processing time. The main time is spent on creating the indexes which is understandable since it is working on the database on the external drive. The import was successful despite taking a long time.

My question is about when I use Mapnik to render an svg of a defined boundary. The rendering works but takes a long time and I can see that nearly 45 gb of data are read from the external drive.

• Is that normal?
• Do I have to read through the whole database to render a bounding box?