The RAID10 is slowed down by write requests just as it should be. But it is unclear why the arrays have such poor scalability.
This amount of write requests coupled with the controller’s inability to cache them proves to be a hard trial for the checksum-based arrays. They are even slower than the single drive at short queue depths.
Take note that the eight-disk RAID6 is considerably slower than the RAID5 whereas the four-disk arrays are almost equal to each other.
Our formula gives heavier weights to the results obtained at short queue depths, so the RAID5 and RAID6 arrays prove to be slower than the single drive. Take note that the other arrays do not enjoy an overwhelming advantage here.
The general picture is the same when the test zone is limited to a 32GB partition but the speeds are higher now.
As a result, the “fast” arrays, especially the eight-disk RAID0, get further away from the single drive.