Under a higher load the RAID0 arrays show scalability in the number of drives per array, but the speed of the two-disk RAID0 goes down after the 40-percent-writes mark.
The RAID10 array behaves well enough – its speed is smoothly decreasing as there appear more write requests in the stream. The RAID10 is slightly slower than the four-disk RAID0 in the Random Read mode, but in the Random Write mode the RAID10 is faster than the two-disk RAID0. That is, the RAID10 uses an algorithm of alternating the incoming read requests between the drives of the mirror couples.
Unfortunately, we can’t say the same about the second mirroring array. Its speed is always lower than that of the single drive, especially at a high writes percentage.
The diagram suggests that a load of 16 requests is already enough for the TCQ technology to showcase its advantages. When there’s a high percentage of reads, the drive without TCQ is noticeably slower than itself with enabled TCQ.
Well, recalling how the Talon controller “disables” the TCQ support, we should say that these data cannot be an indication of a “significant advantage” of TCQ.
Moreover, the effect of lazy writing becomes more important when there are fewer reads to be performed, and starting from the 60-percent-writes mark the speed of the drive almost doesn’t depend on TCQ.
Our increasing the load further doesn’t cause any changes in the ranks but emphasizes drawbacks in operation of some arrays. The slump in the graph of the two-disc RAID0 has become even bigger, and this array is just a little faster than the single drive, while the RAID1 is always slower than the single drive nearly everywhere in this test. Curiously enough, the drive without TCQ is faster than the drive with TCQ when there are many writes to be performed.
The results of the Talon ZL4-150 controller in the mixed-requests pattern show that the alteration of read requests between the drives of a mirror couple doesn’t work for the RAID1 array, and you can only use this type of array to increase the data security. Alas, a RAID1 won’t have any speed bonuses compared to a single drive.
The RAID10 array, on the contrary, works fine and helps to increase the speed of reading random addresses. The four-disk RAID0 array has a high speed (faster than on any SATA RAID controller we’ve tested so far), while the two-disk RAID0 has problems with high percentages of writes.
Turning TCQ on usually brings a speed gain, but the value of this gain is small compared to the previous test.