The following options are available.
memfrac - value between 0.1 and 0.8. The fraction of RAM that may be used by the program.
tempdir - directory where temporary files are written. The default what is returned by tempdir().
datatype - default data type. See writeRaster
todisk - logical. If TRUE
write all raster data to disk (temp file if no file name is specified). For debugging.
progress - non-negative integer. A progress bar is shown if the number of chunks in which the data is processed is larger than this number. No progress bar is shown if the value is zero
verbose - logical. If TRUE
debugging info is printed for some functions