Comment File system (Score 1, Insightful) 194
There was a paper some years ago about building the file system in such a manner that smaller files were placed on an SSD ( 1 MB) and large files were placed on a harddisk. At that time, SSDs were a lot smaller than today though.
Generally, it can make sense to discriminate your files because they don't all have the same space and access characteristics. Maybe 100 files is taking up 90% of the space compared to the other 9900 files. Maybe it's similar for the access pattern.
Still, for the idea to fly, you need to a robust algorithm and it needs to be clever about the strengths of the hardware. For instance, SSDs aren't so hot at random writes, sadly. Less than 0.1 msec write time would be neat for an ACID database.