The Promise controller has problems with RAID0 at every load, save for high percentages of writes. The problems are not so huge as with the mirror arrays, yet considerable anyway. This controller is especially poor when there is about the same amount of writes and reads. Is it the indication that the controller can’t put the available buffer memory to good use? You can see that the controllers are roughly similar under favorable conditions, i.e. in the right part of the diagram. Yes, the processor frequency and the amount of memory are important, but the operation algorithms are important as well. And Promise should certainly revise them for this controller.
The HighPoint is somewhat better than its opponent with RAID5, too. Both controllers have one peculiarity here, though. The three-disk arrays are faster than the four-disk ones when there are more writes than reads. A 500MHz processor must be unable to cope with four HDDs with a spindle rotation speed of 10,000rpm.
The degraded arrays are again slower than the three-disk arrays of the same time. This is especially conspicuous on the HighPoint controller.
It is the Promise controller that proves to be worse with RAID6 in ordinary operating mode. But when it comes to degraded arrays, the HighPoint overtakes the Promise at write operations, but still loses at reading. Curiously enough, the HighPoint survives the loss of one disk easier than the other controller.
When the queue is increased further to 256 requests, the HighPoint accelerates at reading. The Promise, unfortunately, still shows modest performance, especially under mixed load. It really seems to have big problems working with the request queue.
The Promise shows the same problems at reading and under mixed load when it comes to RAID0. In some cases, the performance of its four-disk array is as high as that of the competitor controller’s two-disk array. That’s a depressing result.
The picture doesn’t change much with RAID5: the HighPoint is still in the lead, and the four-disk arrays still have problems at high percentages of writes.
The overall picture is the same with RAID6, too. But we can see some characteristic points even better now. Particularly, the ordinary array on the Promise controller is considerably faster at reading but slows down under mixed load. The HighPoint delivers higher performance than its opponent with both degraded arrays.