@enlightenedgoth @sickburnbro HDD ZFS pool(s).

Only tapes are somewhat suitable for cold storage and even that needs some maintenance and routine checks. Optical media suffers from delamination, HDDs suffer from silent bit flips and SSDs loose electrical charge and the ability to differentiate between multiple state charges if it is an MLC/TLC/QLC die. Enterprise SLC dies have much higher endurance than any other type, which of course comes with a steep price tag.