SSD is one of the easiest upgrades in your computer when you know the right drive to choose. But, it can be a really complex thing when you don’t have any idea of what to look for. Things can become even worse when you don’t even know the terminologies. So, here is my beginner’s answer to another popular question which is M.2 vs NVMe. Although this isn’t the right question to ask, I am going to clear up all the confusion.
M.2 and NVMe are often used together to indicate fast drives. However, these two are completely different things. M.2 determines the physical properties of components in electronics. NVMe can be called a set of rules to determine how an SSD will interact and transfer data with the CPU. It has the basic application of making the most of the NAND Flash memory used in SSDs. But, the drive has to be using the PCIe lanes for the primary interaction.
M.2 allowed the SSDs to become way smaller than the hard drives and SATA SSDs. On the other hand, NVMe allowed the SSDs to become pretty fast and achieve read/write speeds like 10GB/s on our computers.
What is M.2?
M.2 is an SSD form factor under which there are two main types of SSDs i.e. M.2 SATA and M.2 NVMe. The form factor defines the size, shapes, and other physical aspects of devices and components in electronics.
Any SSD that is sized under the M.2 specifications is called an M.2 SSD. Now, it could either be NVMe or SATA. So, M.2 is just a size specification made for solid-state drives. It is also called the Next Generation Form Factor or NGFF.
The M.2 drives come in five different sizes which are as follows.
| M.2 Size (Form Factor) | Width (mm) | Length (mm) | Description |
|---|---|---|---|
| 2230 | 22 | 30 | Used in ultra-compact devices like tablets and some laptops. |
| 2242 | 22 | 42 | Generally found in small laptops, mobile devices and mini-PCs. |
| 2260 | 22 | 60 | Less common, used in mid-size devices where a longer drive can be accommodated. |
| 2280 | 22 | 80 | The most common size for desktops, laptops, and servers. |
| 22100 | 22 | 100 | Used in specialized applications where space is available for a longer drive. |
So, M.2 drives will have any of these five sizes. However, M.2 never defines their speed, latency, compatibility, price, power consumption, and applications. M.2 just says that your drive is going to be of any of these five dimensions.
With the NVMe drives, you often see this form factor written. Most commonly, you will find drives in the 2280 form factor. For example, the Samsung 990 Pro will have 2280 written on its sales page. So, the 2280 defines its dimensions.
Differences in Notches and Compatibility
Although the M.2 drives share the same dimensions, they can have different connector types. This is important to mention because it determines the physical and software compatibility of a drive on a laptop/desktop.
There are three types of keyings on these drives i.e. M-Key, B-Key, and M+B Key. M-Key is a standard notch for M.32 NVMe drives while the B-Key and B+M Key connectors are for M.2 SATA drives. We can install B-Key M.2 SATA drives in both M.2 SATA and M.2 NVMe slots. But, the M.2 NVMe drive will not work on M.2 SATA-only ports.
What is NVMe?
When you connect any SSD to your system, it connects to the main system through an interface. For NVMe drives, it is the PCIe interface, and for SATA SSDs, it is the SATA interface. But, what is NVMe?
NVMe is a protocol that determines how the data is transferred between the CPU and SSD. Again, the lanes are going to be the PCIe (generally 4 lanes). The connection is the same just like other components such as graphics cards but NVMe allows the host system to make use of parallelism in SSDs. NVMe protocol is specifically designed to reduce the latency as much as possible in the PCIe drives.
NVMe will always work with the M.2 drives which utilize the PCIe interface to connect with the CPU. NVMe is also an interface but it is a logical one. In other words, it works on the software level. When you have a drive connected through the PCIe lanes on your system, you unlock a higher bandwidth than the SATA interface. With the help of NVMe, this high PCIe bandwidth is combined with parallel operations to achieve a very high transfer rate.
Without the NVMe, the system has to use the AHCI protocol which is designed for the SATA drives. The AHCI protocol can not work over the bandwidth of 6 Gbps (600 MB/s in the real world). It has a single command queue with just a maximum of 32 commands at a time.
The maximum command queues with the NVMe protocol is 65,535. Each of these queues can handle 65,536 commands. So, if you multiply these numbers, you have around 4 billion commands at once. NVMe makes the best use of parallelism which is the ability to perform multiple tasks at a time in electronics. SSDs already have the capability to handle multiple read and write commands at a time but NVMe protocol is how the engineers achieve it.
Talking about the difference between M.2 and NVMe
Now, you have got the basic idea of both things. Let me clear it again for you.
M.2 just indicates that an SSD is going to be of a certain size. There are five form factors which we discussed above. M.2 drives can’t have dimensions other than these five. SSDs can be divided into different categories like PCIe generation, brands, and price. But, form factor is one of the main parameters. So, you can say, that the M.2 form factor makes sure that the drives you are buying for your system fit perfectly in your system.
NVMe, on the other hand, is a set of rules for data transmission. It is implemented in your drive’s firmware and also the operating system through the NVMe drivers. It just makes sure that the NAND Flash memory on your SSD is utilized on its top limits. It makes the best use of the multiple cores of your CPU, faster PCIe lanes, SSD controller, and NAND flash to achieve the SSD speeds that we are seeing today.
Can NVMe work without M.2?
NVMe SSDs rely on PCIe lanes for communication with the host system. So, as long as the drive is connected through the PCIe lanes, NVMe will work. Even if you are connecting your NVMe to the PCIe slot with a PCIe riser or extension cable, NVMe will do its job. However, because M.2 provides a direct and nearby connection to the CPU through the PCIe lanes, it is going to give you some advantages in latency and overall performance.
Can there be M.2 without NVMe?
Yes, M.2 ports are used for M.2 SATA SSDs and some other expansion cards. It is just a form factor that can be utilized for many M.2 drives. It isn’t limited just to NVMe drives.
FAQs about M.2 vs NVMe drives?
Can we compare M.2 and NVMe drives?
By comparing M.2 and NVMe, we are actually comparing the size of a drive to its way of communicating with the system. So, this comparison isn’t appropriate.
What are the types of M.2 drives?
M.2 SATA and M.2 PCIe NVMe drives are the most popular applications of M.2. However, you can see Wi-Fi cards and other expansion cards in the M.2 form factor.
If NVMe is for M.2 PCIe drives, what is for M.2 SATA drives?
Just like NVMe is a transfer protocol (set of rules) for M.2 PCIe drives. M.2 SATA drives use the AHCI protocol. NVMe is designed to make the best use of parallelism in NAND Flash memory along with the higher bandwidth of PCIe lanes as compared to the SATA lanes.
What are other SSD form factors besides M.2?
SATA SSDs also come in a 2.5″ form factor that replicates the dimensions of normal 2.5″ hard drives. Also, there are PCIe Add-in Cards, U.2 SSDs, mSATA SSDs, and ball grid SSDs that connect directly to the motherboard.
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