Hybrid Arrays are designed for the mainstream use cases where customers want to consolidate multiple workloads. They happen to use Memory and SSD as cache today and HDD behind because that is the sweet spot for building the best balance of $/GB and $/IOP.

All-Flash arrays believe that SSD takes over the world are are making a bet on technology for high performance.

The reality is that Hybrid arrays do not have to use Flash and SSD. They could use other media. It all depends what enables you to hit the customer sweetspot.

If all capacity moved to Flash tomorrow and all write amplification issues solved their would still be high speed, high cost flash and lower cost higher capacity flash. Good system design would need to design a hybrid solution with caching to satisfy the market for consolidation and centralization of storage at the right price. It would be a hybrid System that was all flash.

The fact is that today Hybrid Storage vendors are focussed on mainstram IT needs and are leveraging the appropriate technology to satisfy the use case and all Flash vendors are focussed on the high performance use case.

Unfortunately it looks like the all-flash guys thought that they would be more mainstream and only competing with traditional stroage vendors and because hybrid solutions are spoiling their party they are trying to sell a religious technology argument for mainstream IT use cases.

And as far as the cost per GB being equal that is baloney. The all flash vendors discount two things:-

1) Data reduction technologies can also work on HDD
2) Many workloads do not dedupe or compress well. In fact those workloads are the fasted growing in capacity

What this means is HDD will be around for a good while and even when/if it disappears you still need hybrid architectures to satisfy the broad set of technology needs.