As a terabyte SSD is enough for everything I need random access to, and hard drives are not particularly reliable for backups storage, I wish we just had cheap reliable tape storage to put backups on. But small-scale tape storages appear to be more expensive per terabyte than HDDs are.
The price of a single HDD is (very roughly) constant, regardless of capacity; the price of an SSD is mostly determined by the amount of flash. In other words, you can cut an SSD in half, but you can't do that to a hard drive.
Flash replaced mini-drives in iPods when the price of "enough" flash (2GB or so) dropped to that of a mini-drive.
SSDs replaced HDDs in laptops when the price of a "big enough" SSD (256 MB?) became competitive with an HDD.
Every reduction in flash cost after each transition was a win for the vendor, since they could keep storage constant and reduce the price. (unlike HDDs, where the price stays constant and the amount of storage goes up)
In each case some users (over-represented here) wanted more storage, and vendors didn't care, or were happy to sell more flash for a price premium.
Enterprise systems aren't single drives, but I believe they still have a concept of "enough" - if the savings from HDD are marginal, or the performance loss from concentrating data on fewer and fewer HDDs becomes too much, they'll switch to pure flash. Anecdotally that's already happening. (also, to be honest, another driver is probably because people like to spend their employer's money on high-tech shiny things, which often pays off better career-wise than saving money)
For the Googles and Amazons of the world there will probably never be a value of "enough", and HDD won't fade until the IOPS/TB ratio becomes ridiculously bad. Maybe not even then, as HDD may still be the best way to store data for a few decades.
> In each case some users (over-represented here) wanted more storage, and vendors didn't care, or were happy to sell more flash for a price premium.
Oh yeah, it really boggles my mind Apple still offers new MacBooks with 256 GB drives (unupgradably soldered on-board!). I can't imagine how insane it takes to be to pay the money it costs for it. Also RAM - 64 GB SODIMM can be bought almost dirt-cheap and they put 8 GB, again - built in the CPU, practically impossible (although some crazy hackers managed) to upgrade.
> hard drives are not particularly reliable for backups storage
This is true when you compare them to media designed for long-term storage. But HDDs aren't all that terrible at it. I recently needed to dig out a 30 year old hard drive to recover some data from it, and it worked flawlessly.
I did the same last weekend. One of 3 old 120 GB HDDs (of one the very best models available ~17 years ago) I last accessed about 4 years ago just didn't come up (it sounds like it tries repeatedly but fails).
