And what about writing?
Writing in small data blocks depends on buffer memory, and the results are proportional to the number of disks in the array. The RAID10 are about two times slower than the RAID0 because the caches are not combined in a mirror because data must be written in sync to both disks in it.
Performance depends on checksum computations in this group of arrays. Every array is slower than the single drive, and the four-disk arrays are faster than the eight-disk ones.
We have problems with scalability on large data blocks where the sequential write speed is important, but the most surprising of all is the four-disk RAID10. It is suddenly slower with large data chunks than the single drive. The eight-disk RAID10 is free from this problem, so it must be due to the specific combination of load and the amount of disks in the array.
The checksum-based arrays catch up at the opportunity to write in full stripes, which lowers the controller’s overhead.
The eight-disk RAID5 and RAID6 go neck and neck. The four-disk RAID5 is expectedly good but the four-disk RAID6 is surprisingly slow with large data chunks. Yes, the controller obviously has problems with some array types built out of four disks.