Wow. Has anyone heard about buffered writes ? And does kernel-level page cache ring a bell ? No fsync was ever used in the benchmarks, therefore, it is never actually hitting the disk. The only good thing about this paper is that the Java and Python listings are available at the end, for everyone to identify the basic flaws in this research.
So yeah, it's faster to write directly to MEMORY than to do a copy before writing to MEMORY.