Understand that disk transfers nowadays typically occur in blocks. 64KB can transfer in virtually the same time as 4KB. The big culprits in slowing down database access in MySQL are TEXT fields, which are typically *not* stored in the same block as the rest of the record. Avoid them, as much as practical, and most of the rest hardly matters.
An optimist sees the glass as half full.
A pessimist sees the glass as half empty.
A realist drinks it no matter how much there is.