Now, let’s do some sequential writing:

And the graphs:

All the arrays reach their maximum speeds at big chunks only, when the controller can split the request up for the drives of the array to process it in parallel. But the RAID0 arrays all reach the same maximum, while the four-disk RAID0 is the fastest at 64 and 128KB requests.

The graph of the RAID1 fully repeats the graph of the single drive, while the RAID10 draws a line which is very similar to the graph of the two-disk RAID0. The RAID5 arrays are the slowest, save for the two biggest request sizes where they reach the level of the RAID10.

Now we enable WB caching and watch for any changes. Now we have 100% writes and this should cause some substantial changes:

The graphs of the RAID1 and JBOD are the same, because RAID1 works like a single drive when there are no read requests. But it is a mystery why the other graphs coincide? Judging by the “smoothness” of the graphs we may suppose that the speed of all the arrays is limited by the speed of the controller central chip (or rather by the data transfer rate between the central chip and the cache memory).

The next patterns simulate real-life loads, let’s see how the controller copes with them.