SSDs had vast improvements in cost over the past decade due to (a) the switch from 2-bit MLC planar NAND to 3-bit (TLC) 3D NAND, and probably (b) the growth of

SSDs had vast improvements in cost over the past decade due to (a) the switch from 2-bit MLC planar NAND to 3-bit (TLC) 3D NAND, and probably (b) the growth of the SSD market - 10 years ago most flash went into iPods, phones, etc., so pretty much all flash chips produced were optimized for that use case, and it cost more to make SSDs out of them. Hard drives spent a decade in the wasteland, with little growth in per-platter capacity (google "superparamagnetic limit" for more info) and gains mostly due to packing more platters by filling the enclosure with helium to reduce aerodynamic drag. (fun fact - cast aluminum is porous to helium, which caused no end of trouble) With HAMR and other recent energy-based workarounds to those density limits, hard drives have a number of years of major TB/$ gains ahead of them, while flash is in the optimizing stage - going from e.g. 96 to 144 3D layers, and diminishing returns (at the expense of big performance costs) going from 3 bits per cell to 4 bits ("QLC") for a 33% boost in capacity. (QLC to PLC only gains an additional 25%, at an even higher cost) If you're managing an exabyte of data or more, HDD is probably an important part of your storage mix for a good number of years going forward - devices are currently maybe 5x cheaper than big QLC drives at the moment, the ratio is probably even better when you price out the systems that house them[*], and HDD $/TB is probably going to improve faster than SSD $/TB for a number of years. I started my career working on Asynchronous Transfer Mode networking; ever since then I'm highly skeptical of anyone saying "our technology will eliminate <entrenched technology X> in five years". Unlike ATM vs Ethernet I think it's quite possible that HDDs will fade to irrelevance in 10-15, but 5 years is ridiculous. If you narrow the statement to "no one will sell 3rd party HDD-based storage systems", it might be true - HDDs will go into AWS, Google, big Ceph deployments, etc. * it's actually a bit difficult to spec a system that doesn't add close to 100% to the cost of the drives themselves for either HDD or SSD, and it also depends on how CPU- and memory-efficient your storage system needs. (e.g. Ceph can be a pig, and note DRAM prices didn't fall in the 2011-2021 decade) There are a number of competitive capacity HDD systems on the market - typically 4U 60-drive machines - while the EL.1 SSD format has just come on the market and you'll probably pay a big premium for systems optimized to house them.