What is an M.2 SSD?

An M.2 SSD is a small form factor solid-state drive (SSD) that is used in internally mounted storage expansion cards. M.2 SSDs conform to a computer industry specification and are designed to enable high-performance storage in thin, power-constrained devices, such as ultrabooks and tablet computers. They are generally smaller than other, comparable SSDs, such as the mSATA.

SSDs are a form of storage media that saves persistent data on solid-state flash memory. Unlike a hard disk drive (HDD), an SSD has no moving parts to break or spin up or down. The M.2 SSD specification was originally known as the Next-Generation Form Factor, but the Next-Generation name was changed in favor of the M.2 name, pronounced M-dot-2.

M.2 is an interface specification that supports multiple protocols and applications such as PCI Express (PCIe) and SATA (Serial Advanced Technology Attachment). M.2-compatible products are not limited to solid-state drives either. The specification also supports protocols such as USB and Wi-Fi and can be used in graphics cards and AI accelerator cards that use the M.2 specification.

The M.2 form-factor specification was defined by the SATA International Organization as well as the PCI Special Interest Group, a consortium of technology industry vendors.

M.2 SSD form factor

M.2 SSDs are rectangular in shape. Generally, they are 22 millimeters wide and usually 60 mm or 80 mm long, although card lengths can be different. The card size is identified by a four- or five-digit number. The first two digits are the width, and the remaining numbers are the length. For example, a 2260 card is 22 mm wide and 60 mm long. Longer length M.2 drives usually hold more NAND chips for extra capacity than the shorter versions. Other sizes include:

  • 2280 -- 22 x 80 mm
  • 2230 -- 22 x 30 mm
  • 2242 -- 22 x 42 mm
  • 2260 -- 22 x 60 mm
  • 22110 -- 22 x 110 mm

The 22 mm width is important to note, as it is the standard for desktops and laptops. An 80 mm or 110 mm length card can hold 8 NAND chips for 2 TB of capacity.

How does an M.2 SDD work?

Even though M.2 can be used in many devices, it's most common to see the form factor associated with SSDs for data storage. M.2 drives do not need a cord to connect to a motherboard. Instead, they are plugged directly into the motherboard with a dedicated M.2 connector slot.

An M.2 SSD can be used with both SATA and PCIe protocols. Serial Advanced Technology Attachment, or SATA, is a standard used for connecting and transferring data from HDDs to computer systems. Meanwhile, Peripheral Component Interconnect Express, or PCIe, is a serial expansion bus standard. PCIe is used for connecting a computer to one or more peripheral devices.

In addition to supporting these protocols and others, M.2 NVMe drives (non-volatile memory express) are supported when PCIe-based. NVMe can accelerate the transfer speed of data between client systems and SSDs over a PCIe bus. The NVMe support was developed to reduce bottlenecks and improve performance. It also allows for more parallel processing for read and write requests. Because of its design, the NVMe support can add up to five times better bandwidth than SATA M.2 models, and should give the computer better performance in tasks like file transfers. To use both M.2 SSDs and NVMe together, a user first must make sure their system can use NVME.

M.2 SSDs can also be either single or double-sided. Single-sided M.2 boards would be used in scenarios where space is limited, such as with ultra-thin laptops. Double-sided chips, however, take up more physical space, but have greater storage capacities.

The device itself will have notches in the end, called module keys, which act as connectors.

M.2 module keys

Keys, the notches in the edge connectors of M.2 modules, can distinguish the types of M.2 products.

M.2 module keys
A list of M.2 SSD module keys, including key IDs, PIN locations and interfaces.

M.2 SSD modules plug into circuit boards through mating connectors on either side. Unlike mSATA, M.2 SSD cards have two types of connectors, also known as sockets: B key sockets and M key sockets. A single card can also have both key types. The type of key determines the number of PCIe lanes the socket supports. A B key holds one or two PCI express lanes, while an M key holds up to four PCIe lanes. The B key edge connector is six pins wide, and the M key edge connector is five pins wide.

For Wi-Fi and Bluetooth wireless adapters, M.2 cards are keyed for A and E slots in a motherboard. Most M.2 wireless cards support both A and E key slots.

M.2 SSD pros and cons

Size and capacity are two of the M.2 SSD's greatest benefits. In a laptop, for example, an M.2 SSD takes up far less space and uses much less power than a standard SATA or SAS interface solid-state drive. However, if massive storage capacity is required in a mobile device, other form factors will likely be a better fit.

M.2's performance is also a key feature. An M.2 SSD based on the NVMe specifications, for example, can read and write at much faster rates than SATA or SAS SSDs.

The M.2 interface is a kind of Swiss army knife of a connector, with the ability to support PCIe, SATA, USB 3.0, Bluetooth and Wi-Fi. So, if a laptop with an M.2 interface is purchased, there will be a lot of configuration options for peripheral gear.

The main drawbacks to M.2 SSD storage are price and lack of ubiquity. Prices for 2.5-inch SATA SSDs have plummeted as they have been produced in greater numbers. Currently, a 1 TB SATA SSD will cost about $100 or less; the price of an M.2 SSD with comparable capacity is about two and a half times the cost of the SATA drive.

Another shortcoming of M.2 SSDs is limited capacity. While 1 TB or 2 TB is probably adequate for most mobile applications, higher capacities will be required for M.2 to find its way into more enterprise storage systems.

How to buy M.2 SSD

The first consideration when planning to purchase an M.2 device for a computer is whether it has one or two M.2 plugs.

M.2 cards are typically used in newer mobile computing devices. Because the form factor is different from mSATA cards, M.2 SSDs are not compatible with older systems. Since it is designed for mobile devices, M.2 may not be a fit for large enterprise storage systems. However, enterprise storage vendors are beginning to incorporate M.2 SSDs in their hybrid and all-flash storage arrays. Even with limited capacities, the size and density of M.2 SSDs still allow storage vendors to pack a lot of high-performance capacity into a small box.

If a laptop is compatible with the M.2 specifications, it will have the physical interface, and the device's operating system should already include the required Advanced Host Controller Interface (AHCI) drivers to allow installation of the M.2 storage card. It may also be necessary to make an adjustment in the device's basic input/output system (BIOS) so that it can recognize the M.2 storage.

For desktop computers that are not equipped with M.2 interfaces, there are adapter cards that are available which plug into a PCIe slot to accommodate M.2 cards.

It's becoming more common for flash memory to be used in secondary storage systems. This is done to enable speedier recoveries when computing operations have to switch over to backup or secondary storage during data center outages. Using solid-state drives in secondary systems helps to ensure that business can proceed at an appropriate pace, even when it's running off backup systems.

M.2 vendors

The price of a 2 TB M.2 SSD typically ranges from $230 to $400; lower capacities are considerably less expensive (e.g., 256 GB M.2 SSDs are available for around $50). Samsung, for example, sells a variety of M.2 SSDs in different capacities. Other M.2 SSD vendors include:

  • Toshiba
  • Kingston
  • Plextor
  • TeamGroup
  • Adata and Crucial (owned by Micron Technologies)

In addition, Intel is the largest vendor for M.2 wireless adapters.

M.2 SSD vs. mSATA

M.2 is commonly referred to as an mSATA replacement, but mSATA SSDs still exist and may continue for some time in laptop platforms that support that form factor. Because M.2 and mSATA cards are different and have different connectors, they cannot be plugged into the same devices -- meaning they both still have their use cases.

Micron SSD form factors
Micron M600 SSD form factors (left to right): mSATA SSD, M.2 SSD (22 mm x 60 mm double-sided), M.2 SSD (22 mm x 80 mm single-sided) and a 2.5-inch SATA SSD.

Comparatively, M.2 SSDs are faster and store more data than most mSATA cards. M.2 SSDs support a variety of interface standards such as PCIe 3.0, SATA 3.0 and USB 3.0 interfaces, compared to mSATA, which only supports SATA interface standards. M.2 SATA SSDs have a similar level of performance to mSATA cards, but M.2 PCIe cards are notably faster. In addition, SATA SSDs have a maximum speed of 600 MB per second, while M.2 PCIe cards can hit 4 GB per second.

PCIe support also allows M.2 cards to take advantage of the NVMe protocol. An NVMe drive provides a large performance advantage over drives based on other types of interfaces due to reduced latency, increased input/output operations per second (IOPS) and lower power consumption.

This was last updated in November 2020

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