The reason that SQL Server prefers 64KB NTFS cluster size, this happens to correspond to the way SQL Server allocates storage. One page = 8K, and SQL Server allocates an Extent, which is 8 pages in size. 8 pages x 8KB = 64KB/extent.
Now that we have the math out of the way…
Normally, a default NTFS, formatted drive is 4KB. How to check the current drive cluster size?
Two ways, to check logical drives C & D, open a command prompt as an administrator, copy/paste and run:
fsutil fsinfo ntfsinfo c:
fsutil fsinfo ntfsinfo d:
Note the highlighted part below for the cluster size:
Another simple test, create a small text file on the disk, then open the file properties. The size on disk, will also indicate cluster size:
If you are having disk related performance issues, you may want to consider reformatting your drives to NTFS 64KB cluster size for better performance.