This message was posted on behalf of Intel Corporation
"How RST decides which drive is the source and which drive is the target for the rebuild?"
The Intel® Rapid Storage Technology by default defines which drive is the source and which drive is the target for the rebuild, the algorithm included in the software is intended to make this decision based on the structure on the RAID configuration.
"Is there a way for me to select/change which drive is the source and target?"
Once you have the RAID configuration set there is no way to select or change the source or target storage unless you start the RAID configuration from scratch.