What is the whole M.2 business

[Reizo]

First of all: Sorry for the vague title but I am not really able to make it more precise.
My problem is understanding the whole matter around M.2, (x2/4x) PCIe, SATA, SATA express, NVMe, U.2 and M/B Keys.
I have read SO MANY article about this whole business and I guess i am not dull but still I can't see all the differences and relations of these terms. It sometimes even seems like they're just randomly thrown together.
Is M.2 just the form factor of connectors? How can I tell if an SSD/Motherboard supports PCI or SATA? What connectors use a SATA protocoll or NVMe protocol? What does x2 or x4 PCI mean? What's the difference in keys? ...

My actual intention is to get a new motherboard with an SSD as 'fast' and 'modern' as possible. So what do I really need to look for in the component's specification?
Would be nice if you answered as if I had no idea of anything concerning M.2 so I might understand it even better.

 

[RealBeast]

Your real choice comes down to M.2 in either SATA or NVMe.

If you want the fastest go with NVMe, but insure that your board can support all of your intended and future devices, as NVMe uses up lanes to the CPU, and some motherboard makers disable a couple of SATA ports or disable SATA Express (which is no big deal as it never took off anyway).

NVMe drives have impressive sequential read/write and IOPs numbers BUT insure that you can put a small heatsink on the device and have airflow going over it to prevent throttling due to heat -- not an issue with SATA mostly because they are slower and don't create the same amount of heat.

And if you have a spare PCIe slot you can get an adapter to add an extra NVMe SSD for future expansion.

 

[SkyNetRising]

Is M.2 just the form factor of connectors?

Yes.

How can I tell if an SSD/Motherboard supports PCI or SATA?

Read motherboard specs.

What does x2 or x4 PCI mean?

It means, how many PCIE lanes are used.

What connectors use a SATA protocoll or NVMe protocol?
What's the difference in keys? ...

https://en.wikipedia.org/wiki/M.2

My actual intention is to get a new motherboard with an SSD as 'fast' and 'modern' as possible. So what do I really need to look for in the component's specification?

Look for NVME SSD support.

 

[Reizo]

Thanks so far, but what is NVMe actually, is it a connector interface, or a protocol? Also what's about the 2x and 4x PCIe lanes does that also count for M.2 slots or only for SSDs that are actually in PCIe slots?

 

[TMTOWTSAC]

This might help you out as far as the nomenclature and what everything does:

https://en.wikipedia.org/wiki/PCI_Express

 

[Reizo]

I think things start to get clearer.
Is it that NVMe SSDs connect to PCIe lanes via a special M.2 slot instead of a common PCIe slot that e.g. GPUs are connected to?
And depending on the motherboard the M.2 slot connects to one, two or four PCIe lanes?