SSDs2024-07-01
M.2 SSDs: Big Performance Comes in Small Packages
Solid state drives
(SSDs) released in recent years have become faster and more capable of handling large
amounts of data. Their full capabilities, however, are being hindered or limited by the
interfaces they are connected to. Serial ATA 3rd generation interfaces, designed for
the much slower mechanical hard disk drives, run with a maximum native transfer rate of
6 Gb/s.
The Mini-SATA (mSATA) interface, though designed specifically to provide the
smallest form factor for SSDs, is limited by the SATA 6 Gb/s link. The M.2 standard, a
specification for internally mounted computer add-in cards, was created to address the
limitations of mSATA and provide more options for small form factor cards, including
SSDs in different sizes and with different capacities. M.2 was originally called the
Next Generation Form Factor (NGFF), and then formally renamed to M.2 in 2013. M.2
improves on the mSATA standard, which uses the PCI Express® Mini Card physical card
layout and connectors. As mSATA's "successor," M.2 provides higher performance and
capacity while minimizing module footprint.
An M.2 SSD module is connected to a host
either through a SATA interface or via a PCI Express (PCIe) lane. Though M.2 supports
both SATA and PCIe, an M.2 module may only be inserted in either one of the two
interfaces, so check your motherboard documentation to make sure that your module fits
and works with the corresponding socket on the motherboard.
Differences Between an M.2
and mSATA SSD
Both are high-performance SSDs designed for small devices such as laptops
and tablets. The mSATA interface used to provide the smallest form factor for SSDs.
However, it is limited by the SATA 3.0 link speed of 6 Gb/s and 1 TB maximum capacity.
The M.2 form factor was borne out of the need for multiple options for small form
factor cards, including SSDs in different sizes and with different capacities, and
possibilities for extending capacities even further. M.2 provides higher performance
while minimizing module footprint. M.2 SSDs come in longer modules and with
double-sided component population, enabling larger storage capacities within minimal
spaces. It requires no power or data cables, making installation complete without the
need for cable management.
M.2 SSDs support both SATA and PCIe interfaces. The SATA
revision 3.2 specification, in its gold revision as of August 2013, standardizes the
SATA version of M.2 as a new format for storage devices and specifies its hardware
layout. For the PCIe version, details are included in the PCI-SIG M.2 Specification
Rev. 1.1.
Physically, they look different and cannot be plugged into the same sockets.
The pictures below show ATP M.2 and mSATA SSDs.
SATA or NVMe?
SATA remains one of the
most widely used interfaces in industrial and enterprise applications, so M.2 SATA
modules are optimal choices for those who want compatibility with existing systems as
well as the convenience of hot-swapping and hot-plugging. M.2 modules designed for a
SATA interface will perform according to the latest SATA 3rd generation standard, which
is up to 6 Gb/s.
Enterprises and client systems with a greater need for speed can take
advantage of the Non-Volatile Memory Express or NVM Express® (NVMe™), an interface
specification developed specifically for NAND flash and next-generation SSDs. NVMe
leverages existing PCIe technology to efficiently support the growing bandwidth needs
of enterprise and client systems. An NVMe-based M.2 SSD module installed on a PCIe x2
lane will run at 15.75 Gb/s, while a module installed on a PCIe x4 lane will run at
31.5 Gb/s – a massive leap in speed and performance.
An M.2 SSD module is designed only
for either a SATA or PCIe interface, not both at the same time, although some systems
may have M.2 sockets that will support either one or both interfaces.
ATP offers both
M.2 SATA and PCIe solutions. ATP NVMe SSDs are designed for a PCIe 3.0 x4
interface.
Size Matters
M.2 modules come in different sizes and can also be utilized
for Wi-Fi, WWAN, Bluetooth, GPS, and NFC.
M.2 SSDs typically come in three dimensions,
which may be deduced from the card name —2242, 2260, and 2280 — "22" represents the
width in millimeters (mm), while the next two digits represent the length, also in mm.
The longer the drive, the more NAND flash chips can be mounted; hence, more
capacity.
In choosing the right size, one has to consider how many SSDs can be packed
into a chassis, as well as thermal management issues, which may be a significant factor
for sustained performance. If the area for dissipating heat is insufficient, it may
result to poor performance and instability in the long run.
The picture below shows ATP
M.2 SSDs in different lengths.
Keys and Sockets
An M.2 SSD is "keyed" to prevent
insertion of a card connector (male) to an incompatible socket (female) on the host.
The M.2 specification identifies 12 key IDs on the module card and socket interface but
M.2 SSDs typically use three common keys: B, M, and B+M. You will find the key type
labeled on or near the edge connector (or gold fingers) of the SSD. Before deploying
M.2 SSDs, determine the type of socket on the host and check the module connector
keying, as each connector should be inserted only in the appropriate socket.
ATP M.2
SATA SSDs are B+M-keyed (can fit in sockets for B-keyed and M-keyed modules), while M.2
NVMe SSDs for PCIe 3.0 x4 lane are M-keyed.
Key ID Pin Location Interface A 8-15 2x
PCIe x1 / USB 2.0 / I2C /
DP x4 B 12-19 PCIe x2 / SATA /USB 2.0 / USB 3.0 / HSIC / SSIC
/ Audio / UIM / I2C C 16-23 Reserved for Future Use D 20-27 Reserved for Future Use E
24-31 2x PCIe x1 / USB 2.0 / I2C / SDIO /
UART / PCM F 28-35 Future Memory Interface
(FMI) G 39-46 Not Used for M.2; for Custom/Non-Standard Apps H 43-50 Reserved for
Future Use J 47-54 Reserved for Future Use K 51-58 Reserved for Future Use L 55-62
Reserved for Future Use M 59-66 PCIe x4 / SATA
Table 1. Module key IDs, pin locations
and interfaces.
Source: "All About M.2 SSDs," Storage Networking Industry Association
(SNIA). 2014.
M.2 connectors on the host are called "sockets." Each socket has a unique
mechanical key, and modules are not interchangeable between sockets. According to PCI
Express M.2 Specifications Rev. 1.1, the sockets are distinguished as follows:
Socket 1
: Connectivity socket for Wi-Fi ® , Bluetooth ® , NFC (near-field communication) or
Wi-Gig.
Socket 2 : WWAN/SSD/Other Socket that will support various WWAN+GNSS (global
navigation satellite system) solutions, various SSD and SSD Cache configurations, and
other yet-undefined solutions. (If the motherboard has a Socket 2 for a WWAN card and
it is not in use, the socket may accommodate a B+M-keyed small M.2 SSD. Please refer to
your motherboard documentation for details).
Socket 3 : SSD Drive Socket with SATA or
up to four PCIe lanes.
Important Notes:
Please refer to your motherboard documentation
to make sure that your M.2 module fits and works with the corresponding socket on the
motherboard.
M.2 modules are neither hot-swappable nor hot-pluggable. Performing
hot-swap or hot-plug may damage the modules and cause harm to the person performing
this .
Conclusion
As SSDs continue to revolutionize the way enterprises handle data,
choosing the right storage media in the right form factor and their corresponding
interfaces will be critical. M.2 SSDs offering smaller, faster and more efficient
storage enlarge the range of choices and solutions to match workloads with price and
performance.
For more information on ATP's M.2 SSDs, visit the ATP website or contact
an ATP Distributor/Representative in your area.
