Hive should be able to configure all intermediate MR jobs to write to HDFS, but the final MR job to write to S3.
This will be useful for implementing parallel renames on S3. The idea is that for a multi-job query, all intermediate MR jobs write to HDFS, and then the final job writes to S3. Writing to HDFS should be faster than writing to S3, so it makes more sense to write intermediate data to HDFS.
The advantage is that any copying of data that needs to be done from the scratch directory to the final table directory can be done server-side, within the blobstore. The MoveTask simply renames data from the scratch directory to the final table location, which should translate to a server-side COPY request. This way HiveServer2 doesn't have to actually copy any data, it just tells the blobstore to do all the work.