3TB NTFS Volume Allocation Unit Size

@acejavelin!

It really depends on the files you plan to store on that 3 TB HDD. However, it's highly recommended to use the default 4K for any NTFS hard drive that is smaller than 16 TB.

Just like @whs mentioned, smaller allocation unit size would make sense only if you're keeping small doc files (for example) This way a very small portion of the HDD space will be wasted. If you plan to back up massive data like HD videos, photos, movies, etc., then even bigger than the 4K default AUS would be better.

I'd suggest you to read through this article about the Allocation Unit Size Differences

Good luck. Hope this helps. :)