I wonder if faster SSDs would help?
In particular you can still get used Optane SSDs on eBay, although they’re fairly pricey. (not the bogus m.2 ones that are slower than a halfway decent consumer NVMe)
In particular you can still get used Optane SSDs on eBay, although they’re fairly pricey. (not the bogus m.2 ones that are slower than a halfway decent consumer NVMe)
They may have more M.2 sockets but usually except for the first all the others share the same PCIe 4.0 path.
Those 2 M.2 SSDs have a theoretical maximum aggregated throughput of 24 GByte/s, but what is achievable in practice is typically only slightly above 20 GB/s.
If you have 1 or 2 USB 4 / Thunderbolt 4 ports, the aggregated throughput can be increased with external SSDs, like in TFA.
With 2 internal SSDs and 2 fast external SSDs, a higher throughput than in TFA is possible.
What actually moves the barrier is how fast the slowest of 16 concurrent whole-file reads completes: more drives on direct ports, stable tail behaviour under load, and scheduling. Our ladder shows even that with diminishing returns (one drive ≈52% of four, three ≈90%).
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 need to read twice more data from the twice faster SSD.
In general, you must distribute the data so that the amounts read from each SSD are proportional with the throughputs of the SSDs.
One could write a modified RAID0 device driver, which would use unequal stripes, with widths proportional with the SSD throughputs, but I am not aware of any such already existing RAID0 driver.
mdadm --create /dev/md0 --level=0 --raid-devices=3 /dev/nvme0n1p1 /dev/nvme0n1p2 /dev/nvme1n1p1
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.