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Multithreaded Read & Write Patterns

The multithreaded tests simulate a situation when there are one to four clients accessing the virtual disk at the same time – the clients’ address zones do not overlap. I will discuss diagrams for a request queue of 1 as the most illustrative ones – the speed doesn’t depend much on the number of applications at a request queue of 2 and longer.

The full results can be seen by the following links:

The ASR-3405 is the best controller for multithreaded reading. It is superior irrespective of the array type which means that the others have problems with reading from the RAID0 under synthetic load. It will be interesting to compare this with the results of the real-life FC-Test. The speeds of the ASR-44300 and AAR-1430SA are fantastically low. Hopefully, it is just the controllers’ dislike of the synthetic load.

The reading of two threads produces odd results. The ASR-3405 still boasts the highest speed, but only with the RAID5. With this array the controller’s speed declined only twofold whereas with the (theoretically) fastest RAID0 its speed declined fourfold! Interestingly, the AAR-2820SA+RAID5 combination is not affected much by the addition of the second thread. The other arrays types do not lose much speed on this controller, either. So, we have an odd situation: the RAID5 arrays are faster than the RAID0!

As for the results of the ASR-44300 and AAR-1430SA with the RAID10 array, they are overall good. Although these controllers are still the slowest, the numbers are not depressing anymore.

The ASR-3405 loses its ground when another thread is added. Its results are among the worst in comparison with the same arrays on the other controllers. The AAR-2820SA is the leader now. It delivers similar speeds with every array type, surpassing all of its opponents.

The ASR-3405 is slower than the others irrespective of the array type now. The AAR-1420SA has got worse with the RAID0, being as fast with the RAID0 as the opponents with the RAID10. The AAR-2820SA is in the lead still.

Let’s check out writing now.

It’s the same as at reading when the controllers worked with one thread: the ASR-3405 is the leader. The ASR-44300 и AAR-1430SA are very slow with the RAID10.

Adding a second thread leads to quite different results than at reading. First, the controllers don’t slow down much. Second, the RAID0 is the fastest array type with each controller, just as the theory tells us (but the RAID5 manages to outperform the RAID10). The ASR-44300 and AAR-1430SA have become faster with the RAID10, but not much.

The RAID5 arrays lose their ground at writing three threads and become slower than any RAID0. It would be a perfectly theoretic situation if the RAID10 were not slower than the RAID5. Interestingly, the AAR-2820SA doesn’t show fantastic speeds as it did at multithreaded reading while the ASR-3405 is not slow, being somewhere in the middle with the RAID0 and among the leaders with the other array types.

When the number of thread is increased to four, the AAR-1420SA slows down with the RAID0 while the ASR-3405 is superior to its opponents irrespective of the array type.

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