Sequential Read and Write Patterns

Now let’s look into sequential reading and writing.

As you already know, Intel IOMeter is sending a stream of read/write requests to the array with request queue depth = 4. Every minute the size of the data block changes, so by the time the test is over, we can see the dependence of the linear read/write speed on the data block size. The results (the dependence of the controller data transfer rate on the size of the data block) are summed up in the tables below. We will first look at WriteBack mode:

Now let’s check the graphs showing the dependence of the controller read speed on the size of the data block:

Looks like there is a conflict between the controller read ahead algorithms and our workload…

Let’s compare the results obtained for the sequential reading on 4-HDD arrays in WriteBack and WriteThrough modes: