How much would it cost for every NVMe drive to have a non-volatile cache?

How much would it cost for every NVMe drive to have a non-volatile cache?

You can get various forms of flash with different block sizes; the smaller the blocks, the more expensive it becomes per byte, and the faster you want it, the more expensive it gets.

But the problem is that you don't have just 4K of updates at a time to handle - a high performance NVMe drive is handling gigabytes of unwritten data in its volatile cache, and having gigabytes of very fast flash is expensive, as compared to gigabytes of RAM, gigabytes of reasonably fast flash, and a supercapacitor to let you flush the RAM to the fast flash before you lose power completely. However, even that's going to be significant - doing it with pSLC flash will add maybe $30 to your $100/TiB NVMe SSD, more if you want a bigger cache (useful for performance).