M.2 nvme uses PCIe lanes. In the last few generations both AMD and intel were quite skimpy with their PCIe lane offering, generally their consumer CPUs have only around 20-40 lanes, with servers getting over 100.
In the default configuration, nvme gets 4 lanes, so usually your average CPU will support 5-10 M.2 nvme SSDs.
However, especially with PCIe 5.0 now common, you can get the speed of 4 PCIe 3.0 lanes in a single 5.0 lane, so you can easily split all your lanes dedicating only a single lane per SSD. In that configuration your average CPU will support 20-40 drives, with only passive adapters and splitters.
Further you can for example actively split out PCIe 5.0 lanes into 4x as many 3.0 lanes, though I have not seen that done much in practice outside of the motherboard, and certainly not cheaply. Your motherboard will however usually split out the lanes into more lower-speed lanes, especially on the lower end with only 20 lanes coming out of the CPU. In practice on even entry-level boards you should count on having over 40 lanes.
As for price, you pay about 30USD for a pcie x16 to 4 M.2 slot passive card, which brings you to 6 M.2 slots on your average motherboard.
If you run up against the slot limit, you will likely be using 4TB drives and paying at the absolute lowest a grand for the bunch. I think 30USD is an acceptable tradeoff for a 20x speedup almost everyone on this situation will be taking.
If you need more than 6 drives, where you would be looking at a pcie sata or sas card previously, you can now get x16 pcie cards that passively split out to 8 M.2 slots, though the price will likely be higher. At these scales you almost certainly go for 8TB SSDs too, bringing you to 6 grand. Looking at pricing I see a raid card for 700usd, which supports passthrough, i.e. can act as just a pcie to M.2 adapter. There are probably cheaper options, but I can’t be bother to find any.
Past that there is an announced PCIe x16 to 16 slot M.2 card, for a tad over 1000usd. That is definitely not a consumer product, hence the price for what is essentially still a glorified PCIe riser.
So if for some reason you want to add tons of drives to your (non-server) system, nvme won’t stop you.
how many M.w slots do current motherboards have? a useful property of SATA is that it’s not rare to have 6 of them
M.2 nvme uses PCIe lanes. In the last few generations both AMD and intel were quite skimpy with their PCIe lane offering, generally their consumer CPUs have only around 20-40 lanes, with servers getting over 100.
In the default configuration, nvme gets 4 lanes, so usually your average CPU will support 5-10 M.2 nvme SSDs.
However, especially with PCIe 5.0 now common, you can get the speed of 4 PCIe 3.0 lanes in a single 5.0 lane, so you can easily split all your lanes dedicating only a single lane per SSD. In that configuration your average CPU will support 20-40 drives, with only passive adapters and splitters.
Further you can for example actively split out PCIe 5.0 lanes into 4x as many 3.0 lanes, though I have not seen that done much in practice outside of the motherboard, and certainly not cheaply. Your motherboard will however usually split out the lanes into more lower-speed lanes, especially on the lower end with only 20 lanes coming out of the CPU. In practice on even entry-level boards you should count on having over 40 lanes.
As for price, you pay about 30USD for a pcie x16 to 4 M.2 slot passive card, which brings you to 6 M.2 slots on your average motherboard.
If you run up against the slot limit, you will likely be using 4TB drives and paying at the absolute lowest a grand for the bunch. I think 30USD is an acceptable tradeoff for a 20x speedup almost everyone on this situation will be taking.
If you need more than 6 drives, where you would be looking at a pcie sata or sas card previously, you can now get x16 pcie cards that passively split out to 8 M.2 slots, though the price will likely be higher. At these scales you almost certainly go for 8TB SSDs too, bringing you to 6 grand. Looking at pricing I see a raid card for 700usd, which supports passthrough, i.e. can act as just a pcie to M.2 adapter. There are probably cheaper options, but I can’t be bother to find any.
Past that there is an announced PCIe x16 to 16 slot M.2 card, for a tad over 1000usd. That is definitely not a consumer product, hence the price for what is essentially still a glorified PCIe riser.
So if for some reason you want to add tons of drives to your (non-server) system, nvme won’t stop you.