a "kvConnection" object indicating where the output data should reside (see localDiskConn, hdfsConn). If NULL (default), output will be an in-memory "ddo" object.
overwrite
logical; should existing output location be overwritten? (also can specify overwrite = "backup" to move the existing output to _bak)
params
a named list of objects external to the input data that are needed in the distributed computing (most should be taken care of automatically such that this is rarely necessary to specify)
packages
a vector of R package names that contain functions used in fn (most should be taken care of automatically such that this is rarely necessary to specify)
control
parameters specifying how the backend should handle things (most-likely parameters to rhwatch in RHIPE) - see rhipeControl and localDiskControl