Performance in Intel IOMeter Database Pattern

We will start out by examining the controller’s processing mixed request streams.

So we are sending a mixed stream of requests for reading and writing random-address 8KB data blocks. By changing the ratio of reads to writes we can estimate how good the controller’s driver is at sorting such requests out.

The results of the controller are tabled below:

The diagrams below show the dependence of the data-transfer rate on the percent of write operations in the request stream for queues of 1, 16 and 256 requests.

Under the linear workload, in the random read mode, all the arrays deliver a similar performance. Their speeds begin to differ when there are more write requests to be performed – the drives’ enabled lazy writing and the array type influence the results.

The speed of the RAID0 array depends on the number of the drives in it, but the gap between RAID0 arrays made of different number of drives is only wide at high write percentages.

The graph of the RAID10 array in fact coincides with that of the two-disk RAID0: the former is only slower than the latter in the random write mode (100% writes).

Curiously enough, the RAID1 array falls behind the single drive at any writes percentages. The more writes there are in the queue, the wider the gap between these two arrays is.

Under a higher load, the RAID0 displays good speed scalability according to the number of disks per array. The three-disk RAID0 scales up somewhat worse that the others, though.

The graph of the RAID10 repeats the one of the two-disk RAID0, like under the linear load. However, there is a difference at 90% of writes and the RAID10 starts slowing down in the random write mode. The graph of the RAID1 has the same shape as under the linear load.

This behavior of mirrored arrays suggests that the current driver/BIOS combo of the Sil 3114 controller does not optimize read requests by alternating them to both disks of the mirror couple. The mirror algorithm doesn’t affect the speed with the RAID10 array, while the controller is definitely slowing down when writing on a RAID1 array.

The load of 256 requests doesn’t influence the rankings at all. The RAID0 arrays are again well-scalable. The RAID10 is identical to the two-disk RAID0, save for the random write mode, while the RAID1 is behind the single drive in all the modes.