In the same way that hard drives didn't kill off tape, SSD won't kill off hard drives. The price differential is too great for many applications and they have different operational strengths and weaknesses.

Tapes have a use case that hard drives do not. Tapes are the lowest cost/GB stored and are more shelf stable than hard drives.

SSDs are higher performance than HDDs and have none of the packaging constraints. Flash storage is going to be put into everything and the economies of scale look quite good.

Storage is scaling but the r/w speeds of hdds aren't keeping up. Following the trend line and we see huge hdds that are functionally useless due to how long it takes to do disk operations.

HDDs only exist above tapes because of their performance. And only exist below SSDs due to cost. Tapes are the floor and SSDs are the quickly lowering ceiling. HDDs are likely to be crushed between.

You might be right, but keep in mind that flash has been scaling due to the shrinking semiconductor feature sizes (and additional layers/etc). So a large part of flash's core R&D & production costs are being spread over all the logic being produced. That has been hitting a wall, so while the capacity/price curves for flash look nice, they likely won't continue, which leaves open the possibility that if rust actually gets a 4-5x boost in the near future the current market trends will continue. SSDs for perf/power/size and mechanical harddrives for bulk nearline storage, leaving tape where its been for the past 30 years, as an archival technology.

Horizontal feature sizes for flash memory stopped shrinking years ago. The continued improvements in density and production cost have been the result of R&D that is very specifically focused on 3D NAND flash memory and has little in common with R&D for logic circuit fabrication.

That said, on the horizon of multiple years, I agree that the future scalability of NAND flash doesn't look quite as promising as HAMR/MAMR for hard drives. How that translates into actual product demand and adoption will probably depend on the relatively unexplored question of how much performance per TB our applications actually need. 40+ TB hard drives might not be fast enough to actually serve as nearline storage for that volume of data without eg. multi-actuator technology that essentially gives you more than one hard drive sharing a common spindle motor. Meanwhile, there's no question that QLC NAND flash definitely has adequate read latency and throughput.

Multi-actuator tech sounds interesting, and I wouldn't be surprised to see drives with 5, 10, 50 or 100 read heads per platter at some point.

With 100 read heads per platter, typical seek time is cut by a factor of 100. That won't let them overtake SSD's, but at least allow them to close the gap.

So far, nobody has announced plans to manufacture hard drives with two read heads per platter, so speculating about 100 heads per platter seems rather unrealistic. The multi-actuator technology that is actually being developed by Seagate still has only one read head per platter, but out of the eight or so platters in a drive, the read heads for four of them will be controlled by one actuator and the read heads for the other four platters will be controlled by the second actuator.

Going all the way to 100 read heads per platter would be insanely expensive and would massively increase drive failure rates, while still leaving them about four times slower for random reads than the slowest $35 SSD on the market. This will never turn into a viable product.

You state that with an unwarranted degree of certainty. You're making the same argument, and mistake, that proponents of 'X is going to kill hard drives' have made for decades.

There have been many 'this will be the death of hard drives' technologies over the decades: zip drives, optical drives, tape drives (there was a time when they were predicted to be everywhere... never happened), CD (then DVD) writers, etc. Not to mention MRAM which has been the hottest tech that hasn't really happened yet for 3 decades. These were all going to be some combination of more durable and/or cheaper per Xb. But they all lacked the one critical advantage that hard drives had: massive economies of scale. Here's my prediction: spinning rust isn't going anywhere anytime soon.

I don't know, SSDs have already replaced HDDs in consumer systems to a far greater extent than any of the things you've listed.

Blackblaze is primarily a backup storage company. Their main bread and butter is relatively cold data storage.

Lots of VPS and similar services offer SSD storage now, and I expect it to grow. The one I use didn't even a non-SSD option, and it was a pretty cheap provider.

SSDs offer orders of magnitude better random IO, I imagine that allows the hosting company to have more clients per storage unit, lowering the effective cost of SSDs.

This isn't true, though.

Seagate and WD are spending mountains of cash to develop technologies like HAMR and MAMR which they expect to take them up to 40TB drives. These technologies require entirely new fabrication processes, etc. Very capital intensive.

Not in the next 10 years. Further than that I don't know. SSD won't be cheaper than HDD per GB in 5 years time, the cost of building Flash and scaling down Flash, Multi Layer Flash, 2.5D / 3D/ 4D Flash ( What ever the manufacture wants to call them ) are also going up. Return of investment is taking longer ( Even with the previous high NAND price ). Moore's Law is dead, and it is not only just CPU.

Theoretically speaking there should be a point where the TCO of NAND Flash would cross HDD. But as NAND scales down, it also reduces its write cycle.

I was never a believer in HAMR, the technologies parent mentioned which Seagate announced in 2012, the idea just seems too unrealistic. The approach WD taking MAMR is much better using Magnetic Field. BPM is also far off, but BPM has been in research for nearly a decade, and MAMR should be here in 2019. All of these R&D will come to fruition in the next few years, where we expect HDD to scale to 100TB in the next 10 years.