Dmitry Tolpeko has a quick but helpful post:
It is highly recommended that you try to evenly distribute the work among multiple tasks so every task produces a single output file and job is completed in parallel.
But sometimes it still may be useful when a task generates multiple output files with the limited number of records in each file […]
I had to cut it off right there to keep from spilling the beans here. Click through for Dmitry’s post to see what setting controls records per file, allowing you to keep opening those Spark output files in Excel.