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.
