NAS plus 80 drive LTO9 Library with drive.

AWS Glacier is serval times more expensive FOR ONE YEAR than an LTO library. And if you absolutely can’t afford to get the data back (around 300-400.000$ with 300TB) you can right away not do it at all.

There is no need to use MAMR for anything up to 24TB, because CMR is possible for those sizes. For 18TB, I would use and have used CMR for years, I have tons of 18TB CMR drives in use.

There are 24TB drives incoming ( https://www.seagate.com/content/dam/seagate/en/content-fragments/products/datasheets/exos-x24/exos-x24-DS2080-2307US-en_US.pdf ), everything below that is available. Only above 24TB MAMR or HAMR will probably be necessary, with 28 TB SMR drives on the horizon.

Rather read the original source, which is way better: https://blocksandfiles.com/2023/11/15/seagate-hamr-drives-come-to-corvault/

Just get the original: Seagate Exos. With a MTBF of 2.5 Mio hours, they are twice as „good“ as Ironwolfs.