When configuring disks for specific performance, especially in SQL and Exchange, it is important to set NTFS disk allocation unit size correctly.  Foe example, The size of files and IO operations call for 64K unit size

 

run the following command from an elevated command prompt:

fsutil fsinfo ntfsinfo <Disk Letter:>

Bytes per Cluster shows the allocation unit size.  Divide by 1024 for KB.

 

This example shows 64K, typical in SQL Data disks:
Disk Allocation Size 64K

Here is an example showing 4K allocation size, typical for system drives and general purpose disks:
Disk Allocation Size 4K