When Samsung released the first civilian SSD in 2006, no one thought that this performance monster overturned the 60-year-long dominant hegemony of HDD in the storage industry in just 10 years and replaced it increasingly. Nowadays, The computer does not install a SSD always feel where is not normal.
The ensuing change is the motherboard hard drive interface, the traditional SATA interface limits the SSD play, for which people have developed a variety of more efficient transmission interface, of which there is now very popular M.2 interface .
In fact, from SATA to M.2, there are many interfaces, was submerged in the trend of technological development, Then we talk about today, M.2 interface, why emerge in the new interface out of the mainstream, M.2 SSD interface is certainly good.
'Slow' interface
We put the time back to 2009, when the chrysanthemum is just a flower, drunk also represents only drink more, when we are busy stealing food, Serial ATA International (SATA-IO) officially released a new version of the norms' SATA Revision 3.0 ', while backward compatible with the old norms, the theoretical maximum transmission bandwidth doubled from 3Gbps to 6Gbps.
As a continuation of the SATA interface, SATA3.0 interface relative to a variety of freshmen mature and reliable technology, compatible equipment, high popularity, and 6Gbps for 2.5-inch SSD is enough, naturally SATA 3.0 interface Become an essential interface on the motherboard.
Today, high-end SSD prices remain high, SSD does not completely replace the case of HDD, I believe SATA 3.0 interface for a long time in the future will still be the mainstream.
But humans do not like to stand still, and soon, SATA Association began to think, how to break through the bottleneck SATA3.0?
SATA-Express, or SATAe, is the solution proposed by the SATA Association SATA-Express is a SATA interface + PCI-Express hybrid, The theoretical maximum bandwidth of up to 10Gbps, Compatible with SATA standard hard drives, but also SATA-Express high-speed SSD interface, each SATA-Express interface can be connected to a SATA-Express hard drive, or two SATA hard drives.
However, we did not see SATA-Express become the mainstream interface now, the reason, First, SATA-Express too occupy the motherboard space, some users even call it a history of reversing, dream IDE era, affecting its versatility in the mobile platform, the second is compared to his competitors, there is no advantage in bandwidth, It is tasteless.
Also during that time, the popular notebook, we began the pursuit of thin, we also began to work hard to do small SSD, so the mSATA interface came into being.
mSATA is a product specification of the mini-SATA (mSATA) interface controller developed by the SATA Association that allows SATA technology to be integrated into a small form factor device while mSATA will provide the same speed and reliability as the SATA interface standard.
However, the promotion of mSATA failed in the end because SSD of masta interface was restricted by the area at that time, the number of particles was limited, and its performance and capacity were hard to match with the contemporary 2.5-inch SSD.
At the same time the small size of the price brought by the expensive, coupled with the SSD was not yet mature development, low cost capacity, most consumers do not buy it, the most important thing is mSATA interface SSD has potential is limited, the major manufacturers quickly Abandoned to promote this interface, began to find other ways out.
summary:
Small interface bandwidth is not enough, lack of performance, enough bandwidth, the interface is too large, people began to realize that you want to achieve large enough bandwidth, versatility, good interface, Must change at the root cause, can no longer hold the SATA interface and AHCI standard minor repairs.
In theory, there are three main aspects to the storage latency of a hard drive, the storage medium itself, the controller, and the software interface standard.
The traditional AHCI standard has always been based on high latency HDD as the standard set, with the rapid performance of SSD has long been impotence. There is an urgent need for an interface standard that is more SSD-aware and developed based on flash memory features, so the NVMe interface standard was born.
Why is the NVMe interface standard revolutionary?
NVMe standard, the full name Non-Volatile Memory Express (non-volatile memory standard), is a specification for PCI-E-enabled SSDs that was first introduced at the 2007 Intel Developer Forum and led by Intel in the same year NVMHCI working group set up.
The NVMe standard for PCIe SSD products effectively reduces the latency of the controller and software interface parts, The most important thing is to allow the SSD to go directly to the PCI-E channel CPU, effectively reducing data latency Secondly, NVMe streamlines the call mode. AHCI needs to read four registers for each command, consuming a total of 8000 CPU cycles, resulting in a 2.5μs delay. NVMe does not need to read the register when executing the command.
NVMe PCIe SSDs reduce latency effectively
And the new agreement can also greatly improve the SSD IOPS (read and write times per second) performance, in theory , IOPS = Queue Depth / IO Delay, so increasing the queue depth can effectively improve the IOPS of the SSD.
The traditional ACHI standard queue depth up to 32, but under the NVMe standard, this value can reach 64000, is 2000 times.
In addition NVMe also joined the automatic power state switch, dynamic energy management, drive-free and other functions, drive wide adaptability, low power consumption.
Significant increase in queue depth
summary:
Contrast the traditional ACHI, NVMe interface standard Can effectively reduce the controller and software interface part of the delay , Significantly increase the IOPS performance of SSDs , But also take into account Low power consumption, wide adaptability to drive Therefore, it can be said that the standard of NVMe interface is revolutionary.
M.2 interface on what break out?
See here, Tell me what seems to understand, M.2 interface because he supports the NVMe standard, will come to the fore, right?
Guess the right half, in fact, support NVMe standard interface, and not only M.2 one, there is more pure PCIe interface and very small U.2 interface, let's talk about this U.2 interface, take a look Why can not he become mainstream?
U.2 formal name is actually called SF-8639 interface, the interface design ideas and SATA-E, that is, as much as possible to use the existing physical interface, but added more protocol support is like NVMe, the bandwidth from PCI- E x2 increased to PCI-E x4, it can be said that U.2 is the ultimate version of SATAe.
U.2 interface can not be bad, but compared to his rival M.2 interface, less generality, and this is actually a fatal for the popularity of the interface, U.2 still need to occupy a specific It is not surprising that the wire or riser card is connected to a desktop or laptop computer, which is especially inconvenient and the U.2 interface is gradually becoming less popular and marginalized.
ASUS MAXIMUS VII HERO has been discontinued
So since the NVMe protocol allows the SSD to go faster PCI-E channel, why can not directly insert the SSD directly on the PCIe interface directly connected to PCI-E channel it, the manufacturers also think of this problem, PCIe interface SSD Naturally appeared.
PCIe SSDs are synonymous with high performance, and although their interface standards are the same as M.2 PCIe SSDs, larger pcb boards make PCIe SSDs larger and more suitable for enterprise-class consumers.
However, the versatility is not as flexible as the M.2 interface, so essentially M.2 PCIe SSDs and PCIe SSDs are starting to diverge in product positioning. M.2 PCIe SSDs are intended for mainstream consumers while PCIe SSDs are for higher-end users Such as business users.
summary:
After reading the reasons for the popularity of each interface, we probably understand, M.2 interface can break out, mainly by virtue of two points: 1, support for NVMe transport protocol, with greater bandwidth, increase SSD IOPS, greatly reducing the SSD's delay . 2, the versatility of the interface than other interfaces that support the NVMe transport protocol is better, compact, more suitable for a variety of mobile platform.
Then you talking about the Niubi M.2 interface, what is what thing?
M.2 is actually a standard connector interface, formerly known as NGFF (Next Generation Form Factor), a protocol promulgated by a PCI-SIG consortium led by HP under the standard designation PCI Express M.2 Specification, designed The purpose is to support multiple modules / cards on the same connector, which supports WIFI, Bluetooth, Global Satellites Navigation and NFC in addition to the well-known SSDs.
M.2 interface, the most important are the following advantages: support for higher rates, high potential; relative to the PCI-Emini card, saving 20% PCB space, saving 15% of the connector height, more compact; support for PCI-E3. 0, USB3.0 and SATA3.0 three current mainstream standards, the interface more 'all-around'.
Small size and support for a variety of mainstream communication interfaces, creating a M.2 super versatility, but also pave the way for the M.2 interface popularization.
In the M.2 module size, the M.2 specification 1.0 defines a total of 11 sizes of modules / card, but the mainstream SSD size only 2242, 2260, 2280 three specifications, the name is also named according to the size of the module, For example, M.2 2242, 22 is 22mm in width and 42 is 42mm in length.
Because the longer the length of the flash memory can be arranged more particles, the greater the capacity, so when you buy M.2 SSD, you also need to look at your motherboard to see what size M.2 module.
M.2 module size 
Mainstream SSD size
Special attention is M.2 connector there are three kinds of Socket, (Socket1, 2, 3), Socket1 which all adopt the welding method and only for 1216, 2226 and 3026 size is not common.
Socket 2 supports SATA, PCI-E X 2 interface while Socket 3 only supports PCI-E x 4 channel , With up to 32Gbps bandwidth, nearly 4GB / S interface transfer speed, 5 times faster than SATA, designed for high-performance storage design.
Now some of the motherboard M.2 interface is compatible with both interfaces, you can walk the SATA channel can also take the PCI-E channel, but some only support Socket3 interface, take the PCI-E channel, so you buy SSD Before, it is very important to make clear M.2 interface of one's own motherboard.
About Socket 3 and Socket 2 SSD interface appearance difference can be seen here -
On the left is a slot that supports 'B key'. The short section is on the left with a 6pin design. When the interface is used together with the 'B key', it is the Socket 2 interface and takes the SATA or PCI-E X2 channel.
The other is a slot that supports 'M key'. The short section is on the right with a 5-pin design. When the interface is used together with the 'M key', the PCI-E X4 lane is the socket 3 interface.
Lite-speed series
M.2 interface SSD must be okay?
If you bought a M.2 SSD interface, it is a SATA channel, then his transmission protocol is still the traditional ACHI, maximum read and write performance and take the SATA3.0 interface, SSD no any! !
Therefore, to differentiate, we call the M.2 interface, a high-performance SSD that supports the NVMe protocol, a NVMe M.2 SSD.
But the same NVMe M.2 SSD, the performance may also be very different, mainly due to two factors: one is the SSD interface type is PCI-E 3.0 or old PCI-E 2.0; the second is SSD Is PCI-E X 4 (Socket 3) or PCI-E X 2 (Socket 2.) The biggest difference is the theoretical maximum bandwidth and interface speed, Xiaobian compiled a form for everyone to understand:
It is easy to see that the PCI-E 3.0 X 4 SSD is the best SSD in theory.
However, Xiaobian is not to say that we only recommend that you buy Socket 3, PCI-E 3.0 X 4 interface, M.2 SSD, of course, this is the strongest M.2 SSD, but also the most expensive M.2 SSD.
The advent of the original SSD to HDD users brought great shock, daily experience has been leaps and bounds, but this NVMe M.2 SSD compared to SATA SSD, in daily use, in fact, will not feel significant differences, Talking about for most everyday ordinary SSD will not be a bottleneck.
Xiao Bian always suggested that you buy on demand, if not heavy work to use, do not often need to read and write large files, or wait until the high performance of NVMe M.2 SSD price more people go, it would be better.
Conclusion:
At IDF 2012, Intel is proposing to launch SSD, a technology that is heavily promoted by NGFF technology, primarily for Ultrabook platforms to further reduce the thickness of Ultrabooks while increasing the transfer speed, replacing mSATA. Started to promote this interface to other areas, M.2 interface can start a prairie fire with the rapid spread of popularity, the next step is the popularity of high-performance NVMe M.2 SSD popularity.
Ten years ago, the soon-to-be-announced 1tb mechanical hard drive marked an astronomical price of 3000, but now it is already installed. With the progress of human science and technology, the cost of the SSD is further reduced. If the NAND flash manufacturing manufacturer no longer encounters the danger, Everyone's computer is plugged in with 1TB of NVMe M.2 SSD day will come soon.
