That's described in the article, that they could be used in Linux, but only as a volume. Apparently (if I read the article correctly) that wasn't optimal for exploiting the higher performance.
As I understand it Linux's VFS and Block layer aren't really designed to exploit the type of throughput and latency that Optane provided.
What I'm curious about is what happened to all the PMem (Persistent Memory) and NVRAM (Non-volatile RAM) work that went into recent Linux kernels and libraries.
I thought that with DAX, it was possible to have a real file system, but access to the actual bits goes straight to the backing storage, not the page cache (as it would with traditional block devices). So the block layer and VFS inefficiencies would not necessarily matter, at least if you can use DAX.
