We are going to compare the arrays by calculating their performance ratings. Since each load has the same probability, the performance rating is the averaged speed of the array under all types of load:

As we have expected, the single hard disk drive is the slowest, while the RAID0 array of 8 hard disk drives is the fastest. We were pleasantly surprised with the RAID10 performance: each RAID10 array of 2n HDDs was always faster than the RAID0 array of respective (n+1) HDDs.

Now let’s compare the results for WriteBack and WriteThrough modes:

Even with only 20% of write requests in the queue, disabling the controller cache slows it down significantly.

Depending on the type of array, the performance in WriteThrough mode is 1.5-2 times lower. So, you have to decide between the reliability and speed…