Earlier quoted context omitted.
When you have heterogeneous SSDs, e.g. you mix PCIe 5.0, PCIe 4.0 and Thunderbolt interfaces, you can obtain a greater throughput by managing in software the distribution of data, than by using RAID0. RAID0 works fine only when all the interfaces have the same speed. If one SSD is twice faster than the other, in order to achieve maximal throughput, you must take care to place the data in such a way so that you will n…
One approach I've seen used is: mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/nvme0n1p1 /dev/nvme0n1p2 /dev/nvme1n1p1 Which is effectively a way to get any positive integer m:n ratioed bandwidth distribution over any number of any sized drives.
This would not work with HDDs, because the time to seek between 2 partitions of the same device would cause abysmal performance, but on SSDs this should work fine, even if some SSD controllers might still have a lower throughput when reading non-sequential pages.