Intel has revealed Optane DIMM and SSD read latency numbers.
Optane DIMMs and SSDs use 3D XPoint memory, which is non-volatile, faster than NAND but slower than DRAM, and based on Phase Change Memory cells.
Intel produces Optane DC P4800X SSDs and Optane DC Persistent Memory (PM), delivered in DIMM format. Optane PM delivers cache line (64B) reads to the CPU and “average idle read latency with Optane persistent memory is expected to be about 350 nanoseconds when applications direct the read operation to Optane persistent memory, or when the requested data is not cached in DRAM.”
In comparison an Optane DC SSD “has an average idle read latency of about 10,000 nanoseconds (10 microseconds).”
That makes the Optane DIMM 28.6 times faster than the Optane SSD.
Back in the NAND world a Micron 9100 NVMe SSD’s write latency is around 30,000 nanoseconds and a Micron P420m SAS SSD MLC write takes 75,000 nanoseconds.
Intel points out that memory sub-system responsiveness is expected to be identical to DRAM (<100 nanoseconds) in cases where the requested data is in DRAM, either cached by the CPU’s memory controller or directed by the application.