Seagate is planning to release 18 and 20TB HDDs in 2020: Digital Photography Review
WP Expanse 20TB 7200 RPM 512e SAS Gen3 3.5-inch HDD – Water Panther
Amazon.com: Western Digital 20TB WD Red Pro NAS Internal Hard Drive HDD - 7200 RPM, SATA 6 Gb/s, CMR, 512 MB Cache, 3.5" - WD201KFGX : Electronics
Why you DON'T want a 20TB Hard Drive - YouTube
Seagate IronWolf Pro ST20000NE000 - hard drive - 20 TB - SATA 6Gb/s - ST20000NE000 - Internal Hard Drives - CDW.com
WD 20TB Ultrastar 7200 rpm SATA 3.5" Internal Data Center
First OptiNAND-based WD HDDs go on sale. 20 TB without SMR - HWCooling.net
Seagate IronWolf Pro 20TB NAS Hard Drive 7200 RPM 256MB Cache CMR SATA 6.0Gb/s 3.5" Internal HDD NE-ST20000NE000 Desktop Internal Hard Drives - Newegg.com
20TB HDD SAS ISE 12Gbps 7.2K 512e 3.5in Hot-Plug | Dell USA