SSD + PCIe = ???

Intel is known for its consistent and active support for Solid State Drive technology, both in terms of creating the SSD devices themselves, and in terms of developing an ecosystem to use them. It so happened that in this very ecosystem, fundamental changes were taking shape right now, connected primarily with the use of PCIe bus capabilities for storage needs. How important will be their result, as usual, time will tell, but the scale of innovations does not allow us to just pass them by. So, in a few words about what is waiting for the SSD in the near future.


Projections of the growth rate of the SSD market, depending on the volume. Source: Gartner

SSD + PCIe = NGFF

As SSDs evolve, they increasingly rest on the limitations associated with their functional ancestors — the hard drives. This also applies to physical dimensions (in reality, SSDs are already “falling out” of the housings of even the smallest HDDs) and data transfer interfaces. Apparently, the time has come to cut the compatibility chains holding the further progress, at least in those areas of digital technology where the old bed has become too procrustous.


NGFF card size 22x110 mm
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A fundamentally new form factor drives, developed by Intel and simply called the NGFF (Next Generation Form Factor) offers a completely different approach for all the above positions. From the point of view of physical arrangement, 5 standard sizes are standardized, from 30 to 110 mm long, 22 mm wide and 2-4 mm thick. As for the connection interface, there are two options here: SATA / 2 PCIe lines (this is called Socket 2) or 4 PCIe lines (Socket 3). To distinguish between the first and second comb, the connector is made asymmetrical with two notches.
As you can see, the drive turned out to be small (in the title picture it is on the palm of the right and mSATA on the left) and fast (up to 4 Gbit / s in the case of Socket 3), which determines the main area of ​​its use - ultrabooks and tablets. However, it can be used in server solutions, for example, in the form of caching devices, or even as a bus for the periphery. As follows from the same photo, NGFF drives exist in the form of real prototypes, and their mass production will begin after the appearance of the corresponding interfaces on the motherboard - additional logic for them is not required to be implemented.

SSD + PCIe = SATA Express || SFF-8639

Naturally, not only ultrabooks, but also more productive computers, such as desktops and servers, suffer from the slow speed of the SATA bus. Apparently, for them, PCIe SSD is currently the only real alternative to the storage used today. How to implement a new generation of storage systems, while maintaining the highest possible compatibility with the old? After all, obviously, the replacement will not happen overnight, if only because of the cost of a PCIe SSD. One of the solutions is SATA Express and SFF-8639 connectors.


On top of the figure is SATA Express, below is SFF-8639.

Both of them, as can be seen from the figure, are combined SATA + PCIe solutions. Compatibility with SAS / SATA is complete - old hard drives will work without problems. For newer, PCIe 2x is available in the SATA Express and PCIe 4x versions for the SFF-8639. In general, the segmentation is as follows: SATA Express is a transitional solution that is costly to the budget, SFF-8639 is a serious server option. In the first case, we have additionally only 2 PCIe lines - this will not give us a stunning increase in speeds, but still allow us to “cheer up” the storage. But 4x in SFF-8639 is already serious, although it is fraught with complication of the wiring diagram, and therefore an increase in the cost of the entire system. Thus, the picture emerges approximately as follows: in conditions when the principal obstacles for overclocking the storage facility are practically removed, the choice of its type will be dictated solely on the basis of the desired quality of service and the available amount of funds.

SSD + PCIe = NVM Express

If you take a closer look, there are more differences between SSD and HDD than similarities. More precisely, the similarity generally turns out only one thing - the function performed, and all the rest - the differences: technological, ideological, etc. Based on this, it can be assumed that host controllers designed in time for hard drives also need to be replaced. This is exactly what is happening now: a new PCIe SSD solution, called the developer community, including almost one hundred of the largest players in the digital industry, NVM (Non-volatile Memory) Express, is replacing the “warm tube” controllers.


Prototype NVMe Controller

NVMe allows SSD to reveal all its positive qualities. We list its main advantages:

• The “sequence” has been significantly increased: up to 64,000 queues are supported, each with 64,000 teams;
• Concurrency and multithreading are drastically improved; for paralleling, blocking and synchronization are not required;
• Managed interrupt management, including MSI in order to prevent the emergence of "bottlenecks" in the way of data flows;
• And, most importantly, the delay introduced by the controller is radically reduced. If for SAS / SATA it was at least 6 ms, then the NVMe test sample already showed a result of 2.8 ms, which is more than two times less!

In the future, NVMe speed indicators will be significantly improved: now the technologically real delay is no more than 1 ms, and the developers of the standard talk about the future 10 μs. A comparison of PCIe SSD and NVMe SSD performance is shown in the graph below.



Currently published standard NVMe version 1.1; NVMe drivers are available for Linux, Windows, Solaris and VMWare, UEFI support is coming.

So, as we see, the process of introducing PCI Express technology into the life of storage devices has gone far enough from a technological point of view. Now it's up to the commercial component - how successful will be the introduction of new standards to the market. In any case, there is no longer any way back;