The TL;DR version: Imagine 60x 8TB drives (480TB about 1/2 PB) in a 4U unit or 4.8PB in a rack. Now make those 10TB drives. 600TB in 4U. 6PB in a full rack.
These are shingled drives, great for “cold” storage, object storage, etc. One of the many functions that Unison is used for. These aren’t really for standard POSIX file systems, as your read-modify-write length is of the order of a GB or so, on a per drive basis. But absolutely perfect for very large streaming loads. Think virtual tape, or streaming archives. Or streaming objects.
The short version is that we will use them when they make sense for customers extremely dense systems. The longer version is that you should be hearing more soon about this.
Just remember though that the larger the single storage element, the higher the storage bandwidth wall … the time to read/write the entire element. The higher this wall is, the colder the data is. Which for these drives, is their design point. But you still need sufficient bandwidth to drive these units, either over 10/40/100 GbE or IB of various flavors.