Known history. As soon as more powerful computers appear, as soon as processor performance and storage capacity increase, and the user breathes a sigh of relief - “now I have enough for everything, I don’t have to shrink and save”, so almost immediately new needs appear that select more and more resources , new software, which also "denies nothing to itself." Eternal problem. An endless cycle. And the endless search for new solutions. Cloud storage, neural networks, artificial intelligence - it's even hard to imagine what gigantic capacities these technologies require. But let's not be upset, because sooner or later a solution is found for any problem.
One of these solutions was the NVM-express protocol, which, according to experts, has revolutionized the use of solid-state non-volatile memory. What is NVMe and what benefits does it bring with it?
The speed of a computer largely depends on the speed of reading data from media and the speed of processing commands. No matter how high-performance the operating system as a whole is, everything can be negated by a regular hard drive, which causes programs to slow down when opened or “think” when performing large tasks. Not to mention the fact that the HDD has practically exhausted its potential for increasing the volume of information storage and therefore has become unpromising. And the mechanical drive is even more outdated and slowed down the development of computer technology.
And now HDDs have been replaced by SSDs - solid state drives, non-volatile non-mechanical storage devices. The first SSD drives appeared on the market in the second half of the 2000s. Pretty soon they began to compete with hard drives in terms of volume. But for a long time, they could not fully reveal their potential and advantages in speed, parallel access to cells, because the existing interfaces and protocols were built according to old standards designed to support HDD drives via SATA interfaces and even more ancient SCSI (SAS).
The next step in unlocking the potential of non-volatile memory was the transition to PCI-express buses. But for them, by that time, new industrial standards had not yet been developed. And in 2012, the first computers were produced that implemented the NVM-express protocol.
You should immediately pay attention to the fact that NVMe is not a device and not an interface for its connection. This is a protocol, or rather, a specification for a data exchange protocol.
Therefore, the phrase “NVMe drive” is not entirely correct, and the comparison like “HDD - SSD - NVMe” is absolutely erroneous and misleads a user who is just getting acquainted with the topic. It is correct to compare an HDD with an SSD on the one hand, an SSD connected via the SATA interface (using the AHCI protocol) and an SSD connected via the PCI-express bus using the NVM-express protocol, on the other. Comparing an HDD to an SSD is probably not interesting anymore. Everyone understands the difference, and everyone is well aware of the benefits of the latter. Unless to note some (very striking) advantages. Compared to hard drives, solid state drives are smaller and lighter, are silent, and the complete absence of mechanical drives makes them many times more resistant to damage (for example, when dropped) and simply increases their service life.
Comparing the capabilities of an SSD with an old bus and an old protocol and an SSD on a PCIe bus with an NVMe protocol is certainly of much more interest and will be useful to everyone who is used to staying up to date with new products, those who are about to buy a new computer, and even those who, for example, looking for the best hosting.
The SATA interface, as already mentioned, was created for hard drives, the head of which can physically access only one cell at a time. It's not surprising that SATA devices have only one channel. For SSD, this is deplorably small, because one of their advantages is support for parallel streams. The SSD controller also manages initial positioning, which is another significant benefit. The PCI-express bus provides multi-channel operation, and the NVMe protocol realizes this advantage. As a result, data stored on SSDs is transmitted through 65 concurrent control queues, each of which can contain more than 536 commands simultaneously. Compare: SATA and SCSI can only use one queue, supporting up to 65 and up to 536 commands, respectively.
In addition, the old interfaces require two accesses to RAM to execute each command, and NVMe manages to do this in one go.
The third significant advantage is the work with interrupts. The NVMe protocol was developed for modern platforms using multi-core processors. Therefore, it incorporates parallel thread processing, as well as an optimized queuing and interrupt handling mechanism, which allows for a higher level of performance. In other words, when a command with a higher priority appears, its execution starts faster.
Numerous tests conducted by various organizations and experts prove that the speed of NVMe SSDs is on average 5 times higher than when connecting SSDs via old interfaces.
Now about whether SSDs implemented on PCIe with the NVMe protocol are available to everyone. And it's not just about cost. In terms of price, such an implementation is still noticeably higher, although the prices for computer components, as you know, are high only at the very beginning of sales and tend to decrease rather quickly.
We are talking about constructive solutions, about what is commonly called in professional language "form factor". In other words, in what form these components are produced by manufacturers. There are currently on the market three form factors.
First it's called "NVMe SSD". It is an expansion board and plugs into the same slots as the video card. This is not suitable for a laptop. However, as for many desktop computers, since more and more of them are assembled on compact motherboards, where there are more often two or even one PCIe slot (which is usually occupied by a video card).
Second form factor — U2. Outwardly, it resembles a regular hard drive, but much smaller in size. U2 is usually used on servers, so it is hardly worth buying for the average user.
Third - M2. This is the most evolving form factor. It is actively used in laptops, and more recently it has already been implemented on some motherboards for stationary PCs. However, when purchasing an M2 for yourself, you should be very careful, because SATA SSDs are still produced in this form factor.
However, care is also needed when assessing the feasibility of acquiring any of these form factors for yourself. To begin with, you should evaluate whether your laptop or PC motherboard has the necessary slots. And even if they are, whether your computer has a powerful enough processor, because a weak processor will still not let you experience the benefits of an SSD. If you have all this and, moreover, you often operate with large data arrays, of course, NVMe SSD is what you need.
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Source: habr.com