Besides not making sense for that reason, 23GB is small enough to have lots of content fit in the OS' RAM cache.
150GB is going to trash the caches and hit the pages like crazy. I would never even think of this as an "optimization".
I don't get it - data duplication made sense on optical media, where the files could be laid out manually and on consoles you could probably make it so the drive reads "the closest" duplicate. On PC you don't control what sectors the files land in, so how does this help the HDDs?