Some of the disks in the market over the last few years were not well-labeled in terms of revealing their SMR internals, and use larger media caches to disguise write performance issues (at least, until they don't). For example, the Seagate STGY8000400 is an external 8TB SMR drive. But the industry as a whole is moving to host-managed SMR, so hopefully that specific issue with external disks will soon go away.