Let’s compare the read speed from RAID 1 array with the read speed from the JBOD drive, and the read speed from RAID 01 array with the read speed from RAID 0 array of two HDDs. As we remember, some manufacturers alternate read requests between the disk drives of the mirrored pair. This way RAID 1 array during reads becomes very similar to RAID 0 array, and thus its performance can (theoretically) double!
However, as soon as we cast a glance at the graphs, it becomes evident that Promise controller doesn’t resort to any of the tricks. The read speed from RAID 1 array is always lower than from a single hard disk drive, and RAID 01 array is a little slower than RAID 0 array made of two hard drives. Besides, the speed graphs for RAID 1 and RAID 01 arrays show certain drops when the drive work with 64-128KB and 64-256KB data blocks.
Now let’s turn to SequentialWrite:
It is really exciting that the write speed of the array with various caching settings also didn’t differ that much. Although as we have seen in our Dual-Channel SerialATA RAID Controllers Roundup the differences should be pretty significant especially for a Promise controller.
Just look, what a nice picture! I have even shed a few tears: the controller showed ideal scalability. Of course, Maxtor 6L020L0 hard disk drives should be acting as “good boys” during writes, so that the controller is capable of squeezing everything possible out of them.