Let’s start our investigation with RAID 0 configuration:
On the graph with linear workload you see that the controllers got split in two pairs regarding the influence they exert over the RAID array performance. ITE IT8212F and VIA VT6410 got defeated by both Promise controllers in situations with low share of writes among the processed requests. However, as the share of writes starts growing, and reaches 70%, the former losers outperform the rivals from Promise. In fact, the similar results both controllers demonstrate here caught my eye immediately. The two Promise controllers also run very close to one another, although TX2000 gets a little ahead of the counterpart as the share of write requests starts growing. I could conclude that this RAID array runs the fastest of all when we have only write requests to be processed.
The next graph shows how our RAID array behaves when the queue depth increases to 16 requests. The situation is a little bit similar to what we have just seen in the previous case. Again we see that the controllers perform similarly: we have two pairs again.
The results demonstrated by this RAID array with all the testing participants are considerably higher than those we saw under linear workload. I would also like to stress that the performance of our RAID array grows up as the share of writes increases. The array starts running faster when working with ITE IT8212F and VIA VT6410 controllers, rather than Promise controllers, when the share of writes reaches 80%. Among the Promise solutions, TX2000 starts outpacing the 133Lite counterpart with the growth of the writes.
The maximum queue depth reflects all the changes in the performance of our RAID array. Although the “paired influence” of the controllers on the disk subsystem performance is still evident, the situation we observe here differs greatly from what we saw on the previous graph. The RAID array simply dashes forward with Promise controllers. In case of low writes share they prove much faster than the other two controllers.
After that as the writes share keeps growing, the array performance first drops and then rises again as soon as we reach 90% writes. In case of ITE IT8212F and VIA VT6410 controllers, the RAID arrays speeds up gradually together with the writes share increase and when it reaches 90% writes, it shows better performance than with Promise controllers.