Hacker News Reader

Comment by dogma1138 | Hacker News Reader

For sequential reads/write maybe, not for random access which is orders of magnitude slower still.

Too bad Intel killed Optane.

The new Optane is called Storage Class Memory and is coming in CXL format cards without the programmatic dichotomy imposed fatally on Optane.

Isn't that still NAND flash? What we need for really low latency is CXL Optane, as far as I understand it.

Yes. However Western Digital is predicting latency of the same order as Optane DIMMs in this 2016 blog:

https://blog.westerndigital.com/storage-class-memory-3d-nand...

CXL Optane wasn't going to happen because of the necessity for drivers in either block or direct access mode. Couldn't plug and play.

CXL itself is a good reduction in buss latency and there's been virtually nothing other words the occasional battery backed NAND DIMM on any memory buss, so SCL on CXL isn't going to be poor.

I'd like to see the distribution on that 250-5000 nanoseconds claim. The low end of that competes quite well with Optane, but Optane under moderate loads can keep up similar latency for 99.99% of requests.

That 2016 presentation was not referring to any particular storage class memory technology, and merely was reiterating the definition of the category as something in between (and distinct from) DRAM and NAND. Western Digital still has not fully committed to a specific SCM contender or brought one to market. The server ecosystem is far more ready for a viable SCM than it was in 2016 (and CXL is part of that ecosystem readiness and maturity), but we're still missing the silver bullet technology that provides a memory cell with the durability, speed and cost necessary to squeeze between DRAM and NAND.

> CXL Optane wasn't going to happen because of the necessity for drivers in either block or direct access mode. Couldn't plug and play.

Drivers had nothing to do with that. Intel's Optane/3D XPoint could easily have adopted a CXL interface; nothing about the memory technology is tied to NVMe or Intel's DDR4-based proprietary persistent memory module interface. The only reason a CXL Optane didn't happen is because CXL wasn't going to magically make Optane profitable.

> The only reason a CXL Optane didn't happen is because CXL wasn't going to magically make Optane profitable.

What confuses me is that the PCIe Optane drives launched at $4/GB and the second generation was only $2.30/GB on the biggest model.

Those prices gave those drives plenty of price advantage over DRAM. Was that all being sold at a massive loss? Why was DIMM Optane so much more expensive, and would CXL Optane have to be the same price?

Both Gen 4 and 5 drives keep sequential and random in the same order. Frankly this is excellent and the new news is the old news.

Reply on news.ycombinator.com