Hi Fabrice,
Just FYI, the current caching methods downloads tile images and can
easily take a huge amount of disk space. We are hoping that Jonas'
work will client-side rendering possible and once that is the case, we
have a good platform to cache vector tiles instead, which consume a
lot less disk space.
http://jonasdn.blogspot.se/2015/05/client-side-rendering-of-our-map-using.html