Man, that is going up fast, volume that is. Seagate will release its first 20-terabyte hard drives shortly. The shingle magnetic recording based units offer more density but at the detriment of writing speed. 

20TB HAMR disks have already are selling. This year, the company claimed that 22 and 24 terabyte capacity should also be complied with using this heat-assisted technology.  The CEO of Seagate claims the majority of the HDDs used for the bitcoin mining industry in Chia were sold on the second hand market. The currency accounted for just 4 to 7% of demand for exabytes for the firm, reducing the need to boost production. The overall quantity of storage in Chia increased by roughly 5 percent between early July and 22 July, from 29.2 to 31.8 petabytes.

Seagate CEO
We expect to begin shipping 20 terabyte PMR drives in the second half of this calendar year.

20TB drives with SMR from Seagate coming in the next few months