Comment by robertclaus

I did some research in a database research lab, and we had a lot of colleagues working on OS research. It was always interesting to compare the constraints and assumptions across the two systems. I remember one of the big differences was the scale of individual records we expected to be working with, which in turn affected how memory and disk was managed. Most relational databases are very much optimized for small individual records and eventual consistency, which allows them to cache a lot more in memory. On the other hand, performance often drops sharply with the size of your rows.