Memory and Storage

What is Intel Optane Memory: How it Works and What you Need to Know

Intel’s Optane memory is being touted as the next-gen storage standard, succeeding SSDs. But what exactly is Optane, and is it really faster than SSDs and traditional RAM or memory used in computers?

RAM, by definition, is a volatile memory type. You turn off the power and your RAM modules are wiped clean of data. This isn’t a problem though: RAM is volatile by design: it’s meant to act as a high-speed buffer between your storage device and your CPU (which has access to even faster cache memory).

Still, anyone who’s run a read/write benchmark on their RAM has probably wondered what it’d be like if they could use RAM as persistent, non-volatile storage. It’d be fast: orders of magnitude faster than a hard drive, and providing more bandwidth than a PCIe 4 SSD. And since RAM resides on the DRAM bus, latency would be very low. But of course, RAM’s volatile, right? You can’t possibly use it as storage, apart from those ridiculous, battery-powered NVRAM modules.

Intel Optane vs RAM: Which one is Faster?

This is where persistent memory technology—such as Intel Optane—comes into the picture. Persistent memory offers the best of both worlds: it’s solid-state storage that resides on the DRAM bus. This means it offers bandwidth and latency comparable to your standard DDR4 memory stick. But at the same time, it is, (as the name suggests), persistent memory is, well persistent. It retains data after the power’s turned off.

What’s the point of persistent memory, though? With PCIe 4.0 SSDs coming out, offering over a third of the bandwidth of DDR4 in a run-of-the-mill M.2 form factor, why would we need exotic, RAM-like storage? Well, for starters, commercially available persistent memory (basically the Optane range today) offers speeds comparable with the fastest SSDs out there, but with far, far better latency. In latency-dependent workloads, persistent memory offers an experience that the laws of physics just won’t allow SSD storage to deliver.

How Does Intel Optane Work: RAM > Optane > SSDs

We’ve spent a considerable amount of time describing persistent memory as RAM-like, but exactly how does it work? Let’s take a look.

Back in 2015, Intel (which moonlights as an SSD maker) partnered with Micron, one of the biggest names in RAM, to work on a new persistent memory storage technology called 3D XPoint, which was subsequently marketed as Optane by Intel and QuantX by Micron. Optane works in a fundamentally different way from either conventional SSD storage or DRAM. Conventional RAM stores data in memory cells. A memory cell, at its most basic, is a single transistor and a single capacitor. Capacitors are essentially tiny batteries that store electrons as a charge. The transistor is a switch here that lets the memory controller read the capacitor’s state: 1 for charged and 0 for discharged.

Optane, on the other hand, doesn’t utilize electron charge/discharge for storage at all. Instead, it works in a way that’s similar to memristors: The tech is based on changes in the material properties of the XPoint substrate that result in different levels of electrical resistance. The result is a high speed and very low latency storage that gives users the best of both conventional storage and RAM.

Intel Optane vs Solid State Drives (SSDs)

How does Optane perform compared to conventional SSDs? Having a look at benchmarks, one thing becomes obvious: Latency is where 3D XPoint really wins relative to conventional SSDs. According to benchmark figures, the Intel Optane 905p has a read/write request latency of just 0.017ms, which is four times less than a standard SSD. Low latency has a meaningful impact on real-world performance. Boot times are much improved. Files open faster, and load times in some games are reduced. Take a look at this latency benchmark. Latency on the Optane 905p is nearly 10 times less than on Intel’s own DC P3520.

Source: Tom’s Hardware

What about bandwidth figures? Optane looks a bit less impressive here but that has nothing to do with the underlying technology. Rather, it has to do with PCIe transfer rates. Existing Optane drives operate over PCIe 3.0, offering max bandwidth between 2000-3000 MB/s. Intel has already stated, though, that it’s working on PCIe 4.0 Optane drives. These will enable far faster transfer rates. Let’s have a look at how Optane performs in the here and now:

Source: HotHardware

In a 4 KiB transfer test, Both the Optane 905p and the Optane 900p delivered similar results—they were a bit faster, but not significantly more so, than Samsung’s best NVMe SSDs. In the here and now, bandwidth limitations over PCIe mean that Optane doesn’t provide ridiculously high transfer rates relative to NVMe. However, it’s important to note that few applications make full use even of NVMe SSDs’ prodigious transfer rates. At these speeds, we emphasize again that latency is what will be more obvious to human users, and Optane drives absolutely kill everything else in this regard.

Types of Intel Optane Memory

Till now, Intel has leveraged Optane in three different ways:

As a caching drive: The very first application of Optane was in mainstream systems as a caching drive. You take 16-32GB of 3D Xpoint Optane memory and shove it in one of the NVMe slots and watch the magic. In short, it’s similar to a secondary form of memory. It prefetches the commonly used data files from the HDD, and when the CPU and memory require it, they copy it from the Optane memory rather than the much slower HDD. This was meant to speed up computers with traditional magnetic storage, rather than SSDs. Here’s a well-explained analogy.

Hybrid SSDs: This takes the earlier model and ramps it up to work with SSDs. Intel started pairing Optane memory as the cache in TLC and QLC based SSDs. While this dramatically reduced the latency and saw some modest improvements in overall speeds, it didn’t work well with large chunks of data files.

Optane SSDs: These are the ultimate Optane drives. They are basically the fastest SSDs you can find on the market with markedly lower latency and sustained read/write speeds over TLC based drives. The downside is that there are still no PCIe 4 Optane drives available while the rest are quite expensive, costing as much as a pre-built gaming PC.

Is Optane the Future?

There are downsides, of course. The main issues are cost and capacity. The Intel Optane 905p, the highest-capacity 3D XPoint-based drive on the market, offers just 960 GB of storage for an eye-searing $1,200. If you want multiple terabytes of Optane storage, you’ll need to shell out frankly ridiculous amounts of cash. Secondly, while memory latency is much reduced—and this has a tangible impact on the user experience, for instance, during booting—actual bandwidth isn’t that much higher than your typical NVMe SSDs. This means that in many use cases, you won’t see a marked performance uplift for the 2-3 times cash you’re shelling out.

Nevertheless, Optane is persistent memory, and it’s been on the market for the past 2 years. It’s debatable as to whether or not persistent memory is the next step that storage technology will take. But if it is, Optane and its 3D XPoint tech offer a taste of that future, right now.

Arjun

Penguin-published author, and journalist. Loves PC hardware but has terrible hand-eye coordination. Most likely to be found playing Total War or watching weird Russian sitcoms.

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