Ever since Intel and Micron announced 3D XPoint™, my phone has been ringing non-stop asking for help understanding the technology and the differences between Optane™ storage and Optane™ memory. The good news is it's fairly simple.
Lets start with Optane™ Storage (pictured below). For those of you that know what a PCIe SSD is, it should look familiar. That's because that's what it is! So what's all the hype about? Well for starters, if you could look under the hood, you'd see that this SSD does not contain NAND like all others SSDs, it contains a new type of memory technology called 3D XPoint™. This new memory technology allows the Optane™ SSD to deliver very low latency (<10us vs. ~100us) and with a much tighter latency distribution. The tighter latency distribution or "5 nines - 99.999%" for Optane™ is roughly an order of magnitude faster than NAND-based SSD's as measured by Anandtech. This is because the new memory technology is much faster to read than NAND and does not require erasure before re-write. Additionally, the 3D XPoint™ technology has higher endurance (e.g., the number of times it can be written before failure) than NAND technology. As such, getting to very high endurance (30 drive writes per day) requires less "over provisioning" (e.g., extra memory) than you'd need with conventional NAND based SSDs. Of course all of this comes at a price which Intel states is ~$4/GB or ~4X NAND based SSDs.
Bottom line: It's a REALLY fast, highly predictable, SSD that will certainly get the attention of those who require and are willing to pay for performance... and there's probably more than you think.
As much as I'm a huge fan of Optane™ Storage, there's just something about Optane™ Memory (other than the poor use of the word memory) that I really love. Perhaps it's because it will ultimately be something every reader will eventually purchase. To explain this, let me give you an example of my recent visit to the online Apple store to purchase a new iMAC. I was like a kid in a candy store as it had been a while since I had "built" a new desktop. As I started going though the options, I of course selected the 27" 5K retina system to start (duh), I then took a look at the CPU options and did what I normally do which is pick the one in the middle. The default storage was a 2TB HDD and was included in the base price. There were several options for various capacity SSDs each adding substantial cost and substantial capacity reduction. The 1TB PCIe SSD option was $700 - almost a third of the entire system cost - and of course was 1TB less than the "as-is" 2TB HDD. Price vs. performance. Well, I decided to spend the $700 and live with 1TB of PCIe SSD storage. While I am VERY happy with the performance of my new iMAC, as it boots in 10 seconds with incredible application launch times, I can't help feeling like I was somehow robbed of 1TB.
So where is all this going and how does it explain Optane™ Memory? It's simple, with Optane™ Memory (pictured below), there should have been a third option. Keep your 2TB HDD, pay ~$75 for the Optane™ Memory, and get SSD like performance. I believe they call that having your cake and eating it too! This is accomplished by using the same high speed 3D XPoint™, over PCIe, and using it as a cache between the CPU and the HDD. It really is that simple. Unfortunatley this option was not available when I ordered my iMAC.
Oh, and regarding the name Optane™ Memory, it's really not memory when it's attached to the PCIe bus. I, instead, will be calling it an SSA which stands for solid-state accelerator because that's what it is. You heard it here first!
Bottom line: It's a high speed non-volatile storage cache that makes your HDD perform like an SSD.