128K Sequential Read
We utilized the C400 array to test the RAID 5 sequential read speed from the ASR-72405. We configured the 16 SSDs into RAID 5 with a 256K stripe size. The read pattern fell into a bimodal pattern, with one extreme hovering around 3,100MB/s, and the higher range topping 6.6GB/s. The majority of the read requests fell into the higher extreme, and our average for the test period was 5,500 MB/s.
With our staggered distribution of read results in the test above, we fully expected a larger latency distribution for the measurement window.
Surprisingly, the range of latency distribution was somewhat tight, with 44% (35,201,326 I/Os) falling into the 4-6ms range, 35% (28,040,901 I/Os) falling into the 2-4ms range, and 15% (12,133,712 I/Os) falling into the 6-8ms range.
4K Random Read
The 4K random read results were impressive, with an average speed of 531,600 IOPS. There was a nice even distribution in the results.
The similarities between the read latency from our RAID 0 4k random read testing and the RAID 5 random read is surprising. They are almost similar in the percentage of I/Os that fell in each category, though the quantity of I/Os differ.
43% (13,802,310 I/Os) fell into the 0.00-.02 range, 15% fell into the 1-2ms range, 13% fell into the .6-.8 range, 11% into the .4-.6ms range, and 10% fell into the .8-1ms range.