NVMe vs. M.2 vs. SATA – What’s the Difference?
Storage, like any other technology, is riddled with jargon and terminology specific to the field. The sheer number of words can be perplexing to the ordinary customer, particularly those who are unfamiliar with computer components.
The distinctions and links between form factors, interfaces, and protocols are some of the most prevalent misunderstandings. It can assist customers to navigate the market as they plan for their next purchase by clarifying what these phrases mean and their relevance in solid-state drive (SSD) design.
What is NVMe?
First, a word about SSDs: they're lightning fast. So fast, in fact, that the SATA III connection that hard drives have historically utilized is the limiting element, not their own technology. Then there's NVMe. NVMe stands for "Non-Volatile Memory Express," and it's an open standard that allows contemporary SSDs to function at their flash memory's maximum read/write rates. In essence, it permits flash memory to function as an SSD directly over the PCIe interface rather than through SATA, which is constrained by slower SATA speeds.
To put it another way, it's a name for the bus that the component uses to connect with the computer, not a new form of flash memory. It also has nothing to do with form factor, which is why NVMe SSDs are available in both M.2 and PCIe card formats. The component is electrically connected to the PC through PCIe rather than SATA in both form factors. Yes, it's perplexing, but bear with us.
Is it true that all M.2 disks are NVMe?
No. It's important to remember that M.2 refers to the form factor. M.2 drives are available in SATA (such as the Crucial MX500 M.2) and NVMe (such as the Samsung 970 Pro/EVO) variants, which refers to the bus they use to interact with other PC components. SATA M.2 SSD drives and 2.5" SATA SSDs have nearly comparable specifications. NVMe M.2s, on the other hand, most emphatically do not, as we'll see shortly.
Explanation of Form Factors
Form factors are a simple concept to grasp; they specify the physical characteristics of an SSD in terms of its size, shape, and connection type. The physical factor of an SSD may already reveal a lot about its inner workings, as the old adage goes, "shape follows function." There are many other form factors, such as M.2, add-on cards, and mSATA, however, in today's world, two are the most prevalent in consumer markets.
2.5SSD: 2.5-inch SSDs are probably still the most popular form factor. A 2.5 Inch SSD was the obvious alternative for consumers wanting to increase their storage at the time they were launched since it used the same form factor as traditional hard drives (HD). 2.5-inch SSDs are generally sold with a SATA interface and require SATA cables to connect to a motherboard in the consumer market. However, 2.5-inch NVMe SSDs are also available for corporate and industrial applications.
M.2 SSDs: The M.2 form factor is the most recent and smallest SSD form factor available. The M.2 was developed to maximize PCB utilization and decrease its size when mounted, based on the mSATA (Mini-SATA) standard. M.2 SSDs don't use cables to connect to the motherboard; instead, they plug directly into an M.2 connection socket. M.2 SSDs can use either a SATA or a PCIe interface, with the latter being the more popular. Although both SATA and PCIe M.2 SSDs appear similar at first sight, their connectors show significant differences; whereas SATA SSDs have B+M keys, PCIe drives only have an M key. Another thing to keep in mind is that other peripherals, like Wi-Fi cards, may use M.2 connections, but their connector keys will differ from those of SATA and PCIe.
Interfaces and protocols: a deeper look
A mix of interface and protocol is used to connect an SSD to a host. The interface is the set of rules, standards, and instructions that define the communication between the SSD and the host system, whereas the protocol is the collection of rules, standards, and commands that define the communication between the SSD and the host system. One of the key variables to consider when purchasing an SSD is the combination of both factors. The performance of a particular SSD is determined by the mix of interface and protocol in terms of bandwidth, latency, and scalability.
AHCI SATA: Serial AT Attachment, or SATA, is the most common interface used to connect an SSD to its host to this day. SATA transfer rates range from 1 gigabit per second for first-generation SATA to 6 gigabits per second for SATA III solutions. The Advanced Host Controller Interface (AHCI) communications protocol is used by SATA to control the connection to its host. Because AHCI was intended for spinning disk technology, it performs poorly when compared to alternative communication protocols like as NVMe. Only one command queue is used by AHCI, and each queue may only transmit 32 commands; IOPs can exceed 100K, and latency is about 6 microseconds.
NVMe PCIe: PCIe, or Peripheral Component Interconnect Express, is a standard for connecting any number of components to a host. PCIe may link graphic cards, Wi-Fi cards, storage, and more, depending on the motherboard. In terms of storage, PCIe takes the place of SATA as the interface with the highest bandwidth. There are now four versions of PCIe, each of which doubles the bandwidth of the preceding. NVMe is a communication protocol that governs the connection between a PCIe SSD and the host computer. NVMe, in contrast to AHCI, was built for flash technology, and hence has greater performance than AHCI. The fact that NVMe can connect directly with the CPU, but AHCI must first go through the SATA controller, is one of the advantages of NVMe over AHCI. NVMe can transmit up to 64K instructions per queue and has up to 64K queues. It boasts IOPs in the million range and a latency of only 2.8 microseconds.
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