I'm curious how endurance is handled in this case. Is there a wear level guarantee when provisioning it? I guess this is applicable to any consumable though this seems to be a pretty expensive one.

That’s part of the design of Optane (née 3DXpoint): it’s supposed to be lower latency than traditional SSD and higher durability. I don’t know enough about the how nor the details to say more, sorry.

This article from Anandtech [1] covers the SSD variant though which states:

> The endurance rating for both capacities is 200 GB/day for the five-year warranty period. Given the small capacity of the drives, this works out to 1.7 or 3.4 drive writes per day, which is considerably higher than normal for consumer SSDs.

[1] https://www.anandtech.com/show/12512/the-intel-optane-ssd-80...

> Optane (née 3DXpoint)

Optane is the brand name for Intel products that use 3D XPoint memory. Micron products that use 3D XPoint memory will be sold under Micron's QuantX trademark, if they ever ship. There's also a possibility that Micron could eventually start selling 3D XPoint memory to other SSD manufacturers, and the resulting products wouldn't bear either Optane or QuantX branding.

The more relevant comparison for endurance may be the enterprise Optane SSD DC P4800X, which was initially released with a 30 DWPD rating but has since been increased to 60 DWPD. Intel hasn't described what kind of error correction that drive is doing under the hood, but it's probably more robust than what the entry-level consumer Optane drives do, and possibly more robust than what the DIMMs can do within their latency budget.

> The persistent part is that it's persistent across reboots.

So does that mean it can be considered persistent like a regular SSD/HDD?

Yes. It's durable storage with a RAM interface. Byte-addressable through conventional CPU load/store instructions. It follows the usual cache coherence protocols for memory, but once it gets flushed, it's stable—just like conventional storage devices.

How much of a problem is the gap for SSD's? Don't those have buffers with enough battery to write out if they lose power?

Sorry, I should have been more clear: the performance gap between DRAM and SSD. This sits in between those.

Yes, don't SSD's have DRAM buffers/cache that make the performance gap less important?

Still a big gap. Random read time from NVMe Flash is on the order of 100µs, whereas service time for reads from this medium are lower. You can get an idea of how much lower based on the QD1 numbers of the SSDs based on it at https://www.anandtech.com/show/11953/the-intel-optane-ssd-90....

On top of that, the DRAM-like form is supposed to much further lower latency by 1) getting rid of NVMe and software overhead and 2) letting you read/write as little as a (64b) cache line at a time. We still don't know what the exact remaining latency is, and I bet the few with access through this program will still be NDAd from talking about it. We also don't know about the price/GB.

Those numbers, esp. price, will have a lot to do with how broad an impact this has at first: you can imagine a scenario where most folks currently building large DBs would find it worthwhile to replace 2/3 of their RAM with 5x as much of this stuff for the same price, though that seems kind of unlikely to be imminent. Or we may find out it's only going to be worth it in some niche applications and the rest of us have to wait some generations before it reaches us (if it ever does).

NVMe Flash is, obviously, still sufficient for a lot of workloads and today is nothing like, say, 2004 when I was writing DB-backed apps and HDD seeks were my bane. Notably, if your OLTP DB can have a lot of transactions in flight at once, or your reporting workload is doing sequential reads, you can take advantage of the very high throughput of modern Flash SSDs when working on lots of I/Os in parallel.