August 15, 2017 at 11:41Intel Optane SSD: Features and Benefits
In early July, we started free testing of Intel Optane SSDs . The promotion is still ongoing, and any of you can take part (for details, see the link above).
The appearance of Optane discs on the market can be literally called a revolution in the field of information storage. In this article, we will talk about what technologies are the basis of new drives and what advantages they provide.
3D X-point: new non-volatile memory
3D X-Point (readable 3D crosspoint) is a new non-volatile memory technology based on a phase transition (Phase-Change Memory, abbreviated PCM).
The words about the revolutionary Intel Optane that were said at the very beginning are much more than just a marketing move: in fact, we are dealing with the first case of launching this type of memory in mass production.
For obvious reasons, Intel does not disclose all the intricacies of 3D X-Point. Moreover, in public statements, the company denies that this memory is based on a phase transition. However, there is indirect evidence (see, for example, a good article on this topic) confirming the opposite. It is possible that the basis of 3D X-Point is some kind of hybrid technology.
Therefore, in the following presentation we will rely on information published in open sources.
Phase Transition Memory: Quick Reference
The idea of memory based on a phase transition is not new: it was put forward by the American inventor Stanford Ovshinsky in the 1960s. In 1970, an article on PC technology was published by Gordon Moore, one of the founders of Intel. Over the past 10 years, attempts have been repeatedly made to begin the production of such a memory, but an obstacle to its widespread use was too large a cell size, as well as too complex a technological process. This problem was solved only now. How exactly - Intel keeps a secret.
To understand how 3D X-Point works, let's recall what a phase transition is.
A phase transition is a transition of a substance from one thermodynamic phase to another with changing external conditions. Description of the details is a task that goes far beyond the scope of this article; We refer interested readers to Wikipedia , where everything is explained quite clearly and in detail.
Substances capable of undergoing a phase transition include the so-called metalloids (they are also called semimetals , and this term is used more often in Russian literature) - chemical elements that have the properties of both metals and non-metals. At room temperature, metalloids are insulators, and when heated they have electrical conductivity. Boron is usually used for doping, silicon - for the manufacture of standard transistors.
Other semimetals capable of undergoing a phase transition and used in industry are germanium, arsenic, antimony, and tellurium. The compounds of these substances with metals produce the so-called chalcogenides. If they are mixed in the right proportions, they will have the following properties (the picture was taken from Pcper.com ): Pcper.com
illustration The metalloid
alloys can go from one state to another, and the resistance changes. In an amorphous state, they are more like glass, and in a crystalline state, metal.
In two states, the characteristics of electrical resistance are different: an amorphous phase with a higher resistance (logical unit), and a crystalline phase with a lower resistance (logical zero). Due to this property, chalcogenides are good material for recording information. Actually, they have long been used for this: CD-RW and DVD-RW discs are made from materials based on chalcogenides.
Here is a table in which the memory based on the phase transition is compared with other types of memory (taken from here ):
| Property | PCM | Erprom | Nor | Nand | DRAM |
|---|---|---|---|---|---|
| Non-volatility | Yes | Yes | Yes | Yes | not |
| Minimum element size, nm | <10 | ~ 4x | ~ 3x | ~ 1x | ~ 2x |
| Bitwise data change | Yes | Yes | not | not | Yes |
| Erase cycle required | not | not | Yes | Yes | not |
| Write speed | ~ 100 MB / s | ~ 30 Kb / s | ~ 1 MB / s | ~ 20 MB / s | ~ 1GB / s |
| Read speed | 50 ... 100 ns | ~ 200 ns | 70 ... 100 ns | 15 ... 50 μs | 20 ..80 ns |
| Number of rewrite cycles | 10 6 ... 10 8 | 10 5 ... 10 6 | 10 5 | 10 4 ... 10 5 | not limited |
3D X-Point: Key Specifications
Having considered the general principles of memory operation based on a phase transition, let us turn to the description of the 3D X-Point device. Let's start with the analysis of technical characteristics (here we rely on the materials of the TechInsights website ).
The size of the 3D X-Point memory module is 17.6 × 13.7 mm (241.12 sq. Mm); the only X-Point memory chip is located inside. The crystal is 16.16 millimeters long and 12.78 millimeters wide. The memory efficiency on the chip is 91.4%. This is more than the same value for Samsung 3D 48L V-NAND (70%) and Intel / Micron 3D FG NAND (84.9%).
The data recording density of the 3D X-Point memory is 0.62 GB / sq. Mm, which is much lower than many 2D NAND and 3D NAND memory modules on the market. For comparison: Toshiba / San Disk has a data recording density of Toshiba / SanDisk and Samsung 3D 48L TLC NAND 2.5 Gbit / mm², while Toshiba / SanDisk 2D TLC NAND has 1.28 Gbit / mm². Moreover, the value of this indicator in DRAM is almost five times lower.
There is every reason to believe that the memory modules based on 3D X-Point in the near future will be widely used.
On the same TechInsights website, a photograph of a 3D X-Point memory module chip was recently published: TechInsights
illustration
As you can see, everything is arranged quite simply: pairs from the selector and the memory cell are located at the intersection of two perpendicular rows of conductors (hence the name crosspoint, i.e. intersection) - bit (bitline) and dictionary (wordline) buses. When voltage is applied, the selector is activated, as a result of which reading or writing takes place.
The cells in the crystal are arranged in several layers - hence the abbreviation 3D in the name. The first generation 3D X-Point has a two-layer structure and is available in a 20-nanometer process. Compared to NAND, the cell packing density of 3D X-Point is 8 to 10 times higher.
Phase transition memory is much faster than traditional flash memory. Experiments show that the recording time in one cell of PCM memory is 19 nanoseconds (for comparison: recording in one cell of flash memory takes several milliseconds).
An important plus of this memory is its longevity: if flash memory can withstand up to 10,000 rewrite cycles, then the 3D X-Point memory - up to 100,000,000 cycles!
Intel Optane SSD: Practical Benefits
The previous part of the article was devoted to questions of theoretical aspects: we talked about 3D X-Point technology. We now consider practical issues and talk about the capabilities and benefits of Intel Optane drives.
Bit memory access
A distinctive feature of flash memory is page-level access: to read or write a small portion of data, you need to manipulate large blocks of memory. This provides low latency, which is very important, for example, for working with busy databases.
In drives based on 3 D X-Point technology, everything is arranged differently: as in DRAM, bit-wise access to memory is possible in them. This allows you to provide 100 times lower latency compared to NAND-memory, completely get rid of garbage collection operations and save energy.
Intel Memory Drive Technology
Optane drives can be used not only for storage and caching, but also for expanding RAM. It is enough to install a special program ^ and the operating system will recognize Optane not as a disk, but as RAM. The system will be able to work with huge amounts of memory - much larger compared to those that provide its architectural features. Data between RAM and Optane will be distributed automatically.
Intel Memory Drive technology can be used, for example, in the field of big data and machine learning: it allows you to store large data sets in memory and provide access to them with minimal delay (see the note on this topic here ).
Increasing memory using Intel Memory Drive technology is also beneficial from a purely financial point of view: 1GB of DDR4 memory costs about $ 10. In the case of Intel Optane, even at current far from low prices, the cost of 1GB will be slightly more than $ 4 - almost two and a half times cheaper!
Durability
The Intel Optane feature is listed on the Intel website: 30 DWPD (drive writes per day). This means that the drive can be filled with information, then erased and rewritten again - and so 30 times.
Intel Optane is well suited for use, for example, as caching disks in cloud storage services or in corporate storage systems: they can withstand any load.
Another important characteristic of disk drives is TBW (Total Bytes Written), that is, the total amount of information that can be written to a disk during its entire life. The value of this feature in Intel Optane is impressive: 12.3 Petabytes.
These figures indicate that the new drives are almost eternal, and fully justify their high price.
Conclusion
As already mentioned, we offer all our users to test drive new drives for free.
The terms of the promotion are simple: you are signing up for testing , we will give you a server with the Intel Optane P4800x on board.
Based on the test results, you publish a report article on your website, blog, or on any thematic resource.
And if you write a really interesting report, we will consider the possibility of publishing it as a guest post on our corporate blog .