The drive firmware and layout are more sophisticated than you're imagining: All SMR drives have some non-SMR (CMR) zones for buffering and metadata. For the arc

The drive firmware and layout are more sophisticated than you're imagining: All SMR drives have some non-SMR (CMR) zones for buffering and metadata. For the archival drives I was looking at a while ago (host-managed), it was usually 1% or 0.5% of the total. I would imagine these stealth-drive-managed ones have even more, maybe a few percent, to allow more buffering and hide the cost of shuffling data.