M.2 SSD info

M.2 SSDs come in 3 different physical sizes :

• ‘2230’ : 22mm wide, 30mm long
• ‘2242’ : 22mm wide, 42mm long
• ‘2280’ : 22mm wide, 80mm long

An M.2 SSD’s connector has one of two shapes : ‘M key’ or ‘B+M key’ :

M-key are normally NVMe SSDs, which use PCIe x2 or PCIe x4 .

B+M are normally older/slower SATA devices(600 MB/sec) , but you occasionally see NVMe SSDs (usually PCIe x2). B+M SSDs will normally physically fit in a laptop/PC’s M.2 slot, even if it appears to be an M-key slot.

• x4 means that it uses 4 ’lanes’ or channels on the PCI bus instead of 2, so in theory gets twice as much data transferred per second compared to x2 devices.

• The version (‘Generation’) of PCIe determines the maximum speed of the interface :

• Each SSD and each laptop’s M.2 slot has a specification which you can look up online, which shows both the Generation and the number of lanes (e.g. ‘PCIe Gen3 x2 NVMe '
• You can normally use any Gen/speed of SSD in any laptop/PC’s M.2 SSD slot: they will adjust their speed to work correctly, a bit like RAM does. You only need to start looking into the exact spec of M.2 slots & SSDs if you plan to run a very I/O-intensive workload and want to make sure you achieve the maximum possible data transfer rate.
• Gen4 SSDs are ridiculously fast and you’re unlikely to require the performance they offer; Gen3 SSDs are more than fast enough for normal PC/laptop use.

A couple more things to watch out for :

• if you plan to use older SATA SSDs : sometimes a laptop/PC’s M.2 slot doesn’t support SATA : you can only use NVMe SSDs.
• single-sided vs. double-sided SSDs: some M.2 SSDs have chips on both sides, so they are noticeably thicker than single-sided SSDs : this can be an issue in certain slim laptops where space/clearance is limited.