Performance in Intel IOMeter Sequential Read & Write Patterns

The array receives a stream of read/write requests with a request queue depth of 4. Every minute the size of the data block changes, so we can see the dependence of the linear read/write speed on the size of the data block. The sequential read results are listed in the following table:

Here’s a graph that shows the dependence of the controller’s read speed on the data block size:

The arrays reach their maximum speeds at different data block sizes – when the controller can split a big request into several small ones for the HDDs of the array to process these requests in parallel.

Note also that the maximum speed of the four-disk RAID0 is as high as 215MB/s with the Sil 3114 controller – that’s about exactly four times the maximum speed of the single drive. Excellent scalability!

It’s not all that good with mirrored arrays. As you know, some manufacturers use alternation of read requests between the disks of a mirror couple, even at sequential reading. Thus, a RAID1 array becomes more like a RAID0 and the read speed may double, at least theoretically. But the results of our tests suggest that the Sil 3114 doesn’t use such an algorithm. The read speed of the RAID1 is nearly always the same as of the single drive, and the speed of the RAID10 coincides with the speed of the two-disk RAID0.

Sequential writing comes next:

This graph shows the dependence of the controller’s write speed on the data block size:

Again, the arrays reach their maximum speeds at different moments. However, the scalability of RAID0 arrays can only be seen with two- and three-disk configurations. The four-disk RAID0 breaks the rule, reaching only 193MB/s. That’s good in itself, but we had hoped for something better :).

There are no read requests here, and the speed of the RAID10 is far below the speed of the two-disk RAID0 at big requests. The speeds of the RAID1 and the JBOD coincide. That is, the mirror algorithm slows down the execution of write requests only in the “complex” RAID10 array at sequential writing.

Now, let’s turn to patterns that simulate real-life working environments.