Simple definition
Storage block size defines the unit used to transfer or allocate data and affects space efficiency and performance.
Purpose and use
Block size defines a processing or allocation granularity at a particular storage layer.
How does it work?
Device logical blocks, filesystem allocation units and application I/O sizes can differ.
Example and verification
Compare performance measurements using the same I/O size and identify the observed layer.
Points to watch
A larger block does not automatically improve performance; alignment, workload and wasted space can alter results.
In short
Specify which layer’s block size is being discussed before optimizing or comparing.