There’s a cluster function in the raster package!
https://www.gis-blog.com/increasing-the-speed-of-raster-processing-with-r-part-23-parallelisation/
https://www.gis-blog.com/increasing-the-speed-of-raster-processing-with-r-part-33-cluster/
http://r-sig-geo.2731867.n2.nabble.com/Re-Parallel-predict-now-in-spatial-tools-td7586048.html
http://www.timassal.com/?p=1920