Kobe, I am not sure this is a fair comparison because writing a file to IGFS involves 3 operations: updating the metadata cache (empty file creation), actual file writing and then updating the metadata cache again (update the file size). For this use-case I would suggest using single cache puts (the same way you insert data to Oracle) and combine it with write-behind store writing to HDFS, this should give you better latencies.
If you still want to proceed with IGFS, I would try increasing IGFS file block size, see FileSystemConfiguration#blockSize.
