I have a folder on one of my SSD drives that takes 8 to 10 hours to back
up. It is only about 1.4 GB, but it is allocated 2.4 GB of space
altogether, and there are 580,000 files here. Indicates that per file
it's using up a little bit over half of a cluster on average. File
system is NTFS.

Meanwhile, this same drive can backup the remainder of the drive in
under 2 hours, and the remainder of the drive is 390 GB! Is NTFS this
inefficient for small files like this?

Yousuf Khan