Intel Optane memory was based on 3D XPoint technology. In this article, I learned about what is Optane memory and how optane memory works. Read the article, and feel free to share your query.
So Question Raised is what 3D XPoint technology is?
3D XPoint Technology
Let’s start with a summary of the 3D XPoint technology itself (read as “three di cross point”). I apologize right away – we do not currently disclose detailed information about the technology.
Also, the review’s focus will be on the final products rather than on the technology itself.
First, although the technology is a joint development of Intel and Micron, the implementation of the technology in the form of products is separately managed by each vendor.
Thus, I will talk about products based on 3D XPoint relevant only to Intel products.
Secondly, 3D XPoint is not NAND; it is not NOR, it is not DRAM, but a completely different beast.
Without revealing the details of the physical implementation of the memory, I will describe the key characteristics and the differences between 3D XPoint from NAND and DRAM.
- Unlike NAND, there is no binding of write operations to pages and no binding of erase operations to blocks.
- With 3D XPoint, we can access data at the physical level at the individual cell level. Also, we do not need to delete data before the write operation – we can overwrite the data, which allows us to get rid of read-modify-write operations and greatly simplify garbage collection.
- This reduces latency and increases the number of I / O operations per second (IOPS); also, write operations are almost as fast as reading operations. Finally, the endurance of 3D XPoint memory is much higher than NAND (such an effect as electron leakage from cells does not exist here).
- To summarize, 3D XPoint is faster and more durable than NAND. However, Unlike DRAM, 3D XPoint allows you to create devices with a higher density of data storage, is a non-volatile type of memory, and, at the same time, cheaper. Of the drawbacks in this comparison, 3D XPoint as a technology for implementing memory is somewhat slower than DRAM (note that we are comparing technologies, not products based on these technologies).
All of the above concerned 3D XPoint as such – this, however, is less important for users than the characteristics of specific devices based on 3D XPoint.
Thus, our conversation goes on to describe Intel Optane products based on this technology.
In short, this is a brand for all Intel products based on 3D XPoint technology. If we explain in more detail, then Intel takes 3D XPoint “waffles,” conducts its testing and selection of memory chips, independently develops the design of the end device – creates an SSD controller, PCB layout, firmware; tests and validates the end device, brings it to the market – this is all hidden under the words “Intel Optane.”
At the moment, 2 fundamentally different products are officially announced and launched on the market: Intel Optane Memory – for client use models – and Intel® Optane SSD DC P4800X – for server use.
This article will analyze the client product in more detail, while the server product will be the subject of the next review.
So, Intel Optane Memory. The first thing to understand about this product is that despite its name, it is not DRAM, but NVMe SSD in the M.2 2280-S3-BM form factor.
Top view – under the sticker, there is 1 3D XPoint chip (this is a 16GB version, 32GB has 2 3D XPoint chips – the pads for the second chip are visible):
The module is single-sided, so the backside is empty.
The device complies with the NVM Express 1.1 specification. At the moment, 16GB capacities are released on the market (one 16GB 3D XPoint memory chip is used) and 32GB (two 3D XPoint memory chips are used with 16GB each). From the interesting design details:
- The controller is an internal development of Intel.
- The design does not use DRAM.
- Only 2 PCIe gen3 lanes are used, not 4 lanes, as many would expect.
- Declared wear resistance – 100GB of recorded data every day for 5 years.
Now about performance
The performance of the 32GB version is higher because 2 3D XPoint memory chips are used against one chip in the 16GB version.
It would seem that the performance in terms of bandwidth and IOPS is not impressive. The thing is that this performance data was measured at a queue depth of 4 – unlike other SSDs, which are usually measured at a queue depth of 32 or higher.
It is at shallow lines that Optane is most visible. For clarity, here is a graph of the performance of different types of devices at different queue depths *:
Simultaneously, as our internal tests show, the vast majority of tasks that an ordinary user faces at home or in the office have a queue depth of 1 to 4 (for more details, see below).
SSD specifications are written using loads with a queue depth of 32 (for SATA) and more (for NVMe). The difference is obvious.
However, Intel does not position the use of Optane Memory as a regular SSD for obvious reasons – the capacity of the devices is not enough for user tasks (except some interesting options, such as a small but fast and reliable bootable drive for Linux, or scratch disk for Adobe Photoshop, or a small but fast cache with Intel Cache Acceleration Software, or an interesting solution) All the power of the Intel marketing apparatus is aimed at promoting a new acceleration technology (roughly speaking – caching, but this is not an exact definition) of a slow SATA-drive (be it a hard drive, solid-state drive or even some hybrid models) with the fast Optane Memory module.
Imposes restrictions on supported hardware and OS
- 7th generation Intel Core processor or later.
- Intel 200 Series Chipset or later.
- A BIOS integrates the RST UEFI driver version 15.5 or later (15.7 for the X299 chipset series). Yes, BIOS legacy mode is not supported – Optane Memory requires UEFI boot.
- Windows 10 64-bit.
- Intel Rapid Storage Technology Driver 15.5 or later.
- Bootable SATA-drive (Optane Memory will accelerate it). Only GPT markup is supported.
- 5MB of free space at the end of a SATA drive is needed for RST metadata.
- We make sure that the motherboard BIOS supports Optane (see above; now all “Optane Memory Ready” boards on 200 series of chipsets are shipped with BIOS, supporting Optane Memory. However, you can still find boards from previous lots on the market – they will need to be updated with BIOS )
And yes, Intel has done a tremendous amount of work with board manufacturers – all boards that support Optane Memory have such a nameplate on the box:
- We take a system with a SATA drive on which Windows 10 64-bit is installed (the drive must be connected to a SATA port, separated from the Intel AHCI controller in the chipset. Otherwise, RST will not see it). The markup should be GPT.
- The Optane Memory module is connected (the drive must be inserted in the M.2 slot with the separated PCIe lanes from the chipset, supporting the “remapping” of PCIe lines to the Intel AHCI controller built into the chipset).
- The utility is installed. It automatically changes the SATA mode in the BIOS to RST / Optane mode (this requires one reboot of the system). It also enables acceleration using Optane Memory (this requires a second reboot of the system). As a result, instead of 2 disk devices, the system will see only one thing – the so-called. Optane Volume.
- PROFIT! Namely:
- Faster loading of the operating system;
- Speeding up most I / O operations (essentially caching, but with reasonably smart algorithms).
We’ll also talk a little about how this all works.
- Firstly, at the time of activation of Optane Memory, the RST driver will transfer the files necessary for loading the OS and the file table to the fast Optane Memory drive. The key here is just transferring, not copying. The RST driver’s mechanics are such that not all data lying in the cache on the fast device will be copied to the slow device without fail. This increases the overall system performance and also solves the problem of data synchronization.
- However, as you can see, a physical failure of Optane Memory is likely to lead to loss of access to data on the SATA drive. Because data transfer occurs immediately upon activation of Optane Memory, the very first boot of the system will be faster than before Optane Memory (this is especially noticeable if the hard drive is faster than SATA SSD – however,
- Secondly, during the operation of the RST system, the driver will continuously produce caching. And here there is one important difference between Optane Memory modules of different capacities – on a device with a capacity of 16 GB, only caching at the block level is supported, on a device with a capacity of 32 GB – caching at the block level and caching at the file level (both work simultaneously).
- In the case of block caching, the decision to cache a block occurs instantly at the time of the I / O request. In the case of file caching, the driver monitors the frequency of access to files and puts all this in a special table, which then (at the time of system downtime or according to the user’s schedule) is used to determine which files remain in the cache, which are deleted and which are added.
- Both types of caching use fairly clever, in my opinion, caching decision algorithms – I can’t describe them deeply here, but for general understanding, I note that, for example, video files are not cached (yes, the driver looks at the file extension), in consideration the file size is accepted, the type of load is determined – the preference for caching is given to random access rather than sequential access, which makes sense due to the prolonged operation of hard drives on random access operations, etc.
- On the Internet, I met some negative comments on the topic that “the cache will instantly clog up with data,” “16GB capacity is not enough for anything,” and the like – as a rule, these are reviews from people who have never tested Optane Memory. I have not heard negative reviews about the performance of such a solution from any of our partners,
A few critical points.
- If you need to connect the SATA drive to another system when the system acceleration is enabled using the RST driver and Optane Memory, you must either transfer the entire configuration (SATA device + Optane Memory, while making sure that the new system supports Optane Memory) or first turn off acceleration (this is done by pressing a single button in the utility – in this case, at the time of shutdown, the data from the cache will be transferred to the SATA device, the RST metadata will be deleted, the Optane Memory device will be cleared).
- Disk cloning will not work when acceleration is enabled with Optane Memory because no utility can work with RST metadata. Direct cloning of a section with metadata will not be enough – the fact is that the metadata is tied to the serial numbers of the Optane Memory and SATA device. There are no difficulties with backups at the file system level.
Why is it necessary?
Now it’s time to talk more about why all this is needed. Let’s start with a more detailed analysis of the loads experienced by systems of ordinary PC users. Even before the development of the Optane Memory product was completed, as part of the Intel Product Improvement Program, my colleagues conducted a study on what ordinary users do with a computer at home and work. Results – the number of actions of various types performed by users (averaged data for 1 day of using a PC):
All these events are closely related to the performance of the system drive, and, as a rule, they require random access to data, which hard drives cope extremely poorly. Thus, Optane Memory’s use can significantly speed up the execution of each of the above actions.
However, you ask why I should buy Optane Memory to speed up the hard drive if I can buy 128GB SATA SSD for the same money, but the OS and key applications on it, and use the hard drive for other data? Here, on the one hand, the question of convenience is if you have at least some basic skills to be able to choose where to install the OS/applications (I suspect that all GT readers fall into this category.
However, I can assure you that, for example, my parents, like most PC users, are not capable of this). You won’t be lazy to do this for every application (especially problematic for games – with the current requirements for disk space, 128GB will clog under the OS and 1-2 games), then from this point of view, a hybrid configuration of SSD + HDD maybe for Al convenient.
However, keep in mind that with Optane Memory, no manual data transfer is required – as soon as you stop using one application and begin to use another more actively, the necessary data will be quickly added to the cache. On the other hand, let’s recall the graph that I presented above – performance depending on the queue’s depth. In small queues, data access on the Optane Memory is much lower than the SATA SSD. Inside Intel, we measured how deep various applications use the queue – here are the results:
- Queue depth when using applications.
- Queue depth when starting applications.
- Queue depth distribution for a typical corporate user’s working day (measured on Intel employees occupying different company positions).
- Thus, queue depth distribution for different user workloads.
- We have already seen how much better Optane Memory handles work in shallow queues.
- Comparison of system performance with HDD versus the same system with HDD + Optane Memory.
- Another interesting comparison is the same test, but in a system without Optane Memory, there is 2 times more RAM.
And this is a very valid comparison. Although some types of loads require a large amount of RAM, their lion’s share of the requirements for large amounts of memory does not. Thus, it may make sense to put 4 GB of memory instead of 8 GB and invest the money saved in accelerating the storage system for many users.
The Bottom Line
To summarize, I recall that Optane Memory can be used as a standalone SSD, but this is not the main use model. All the magic happens when used as an accelerator for a slow hard drive (or even a SATA SSD) – a relatively small investment of money can speed up the system performance several times on most user loads. This is achieved due to both hardware (Optane Memory has significantly lower access delays compared to other SSDs on the market, performance in small queues is much higher than alternative solutions), and software – the RST driver uses quite advanced logic for caching operations (and in this is the difference from the previous technology – Intel Smart Response Technology).
I am very interested to know the opinion about the product and the solution as a whole from the comments. However, I would like to avoid negative opinions because of a lack of understanding of the solution or lack of experience in using it. If in doubt, ask better before criticizing.
In the next article, we will analyze a server product based on 3D XPoint technology – Intel Optane SSD DC P4800X Series – coupled with the Intel Memory Drive Technology software solution.
* All tests mentioned in this article were conducted internally by Intel. All tests with Optane Memory were carried out on 7th generation Intel Core processors. Queue depth tests using the 6th generation Intel Core processor. System configuration used for tests: