[adgjlsfhk1]

While you can get 24TB ram, there is a pretty big cost difference. 2 TB of ram costs roughly $10000 compared to $130 for NVME storage (or $230 for 12 TB of a good hard drive). Sure the NVME is ~3.5x more expensive, but the latency will be dramatically lower and the throughput will be dramatically higher. Sure you can build a 24 TB ram system, but at that point the cost of the server will be entirely the ram. The reason for NVME based storage at this point is that at only ~3.5x the cost of a hard drive, you can switch all your storage over and as long as you don't need tons of storage (i.e. less than 100TB), the SSDs will be a minority of the cost of the system.

[creshal]

All that applies to regular kv stores abstracted through filesystems and block device layers just fine.

But when your latency requirements are so tight that you cannot possibly afford the latency penalty of a filesystem, you better have a good business case to justify either developing a custom bare-metal-nvme (which is $$$$$ and takes time) or getting a multi-TB RAM system, which is also $$$$$, but far more predictable, and can be put into production today, not 6+ months later when you finish developing your custom kv store.

For the other 99.999% of use cases, sure, just go with NVMe backing your regular virtualization/containerization infrastructure.