Unix Filesystems are allocated a block size upon creation, a block being the unit of data the filesystem will always automatically allocate on the disk. So how does this element affect performance?

A large block size will give the best I/O speed for large files whereas a small block size gives better storage efficiency. In general then, filesystems used for large files should have a large block size since as file size increases, the amount of unused space at the end of the file becomes relatively small. This also makes sense since if you're working with huge files you'll want to access them as quickly as possible, particularly if those files are executables. Large executables in a filesystem with a large block size will have a faster startup time, and paging time.

The question of whether this consideration is redundant stems from the fact that block size applies to filesystems, not directories or files and most practical filesystems will contain a mix of file types. However, dedicated filesystems are not only good practice, but also essential to the management of, for instance, a large database. In the case of a database-dedicated filesystem the block size is a definite consideration. The larger data files and executables should be stored on filesystems with large block sizes, and the areas where smaller files exist, for example development areas will be best served by a smaller block size.

Note that additional refinements can be made by aligning the block size of the database with the filesystem, for example making the Oracle block size the same. This will provide a performance lift to datafile reads and writes.