As the workload increases, we see the arrays show different speeds. The “mirror” arrays perform much faster in the Random Read mode, as no write requests and many random-address read requests allow the TwinStor technology to show its best. Ideally, you get a double gain in the read speed because reading is performed from two drives at a time, accounting for what head is closer to the desired address. As you see, the RAID1 and RAID10 arrays are really twice faster than the single drive and the two-disk RAID0, respectively.

TwinStor is less efficient when there is a good deal of write requests in the queue (that is, there are few read requests). TwinStor only works with read requests, as you know. Thus, it’s no surprise that “mirror” arrays slow down in such operational modes. On the other hand, when there’re many writes, the effect of the WriteBack caching mode is felt stronger, so the mirror arrays even speed up a little. Overall, under the 16 requests workload, the RAID1 is always faster than the single drive, while the RAID10 is in its turn faster than the two-disk RAID0 across all the operational modes.

The speed of the single drive continuously increases as there are ever more writes in the queue. The graphs of the RAID0 arrays have a shape, similar to the graph of the single drive, in proportion to the number of drives in the array. The RAID0 arrays are nearly always faster than other arrays of the same number of drives (except the modes with a high reads percentage where TwinStor strongly influences the performance of mirror arrays). The RAID0 arrays of two and four drives have slumps in their graphs on 10% writes – as you know from our previous reviews (for example, of the Adaptec Serial ATA RAID 2410SA controller), the cache of the hard disk drive is to blame for that.

Read requests are processed with the same speed for the RAID5 arrays and for the RAID0 arrays, but the RAIDs 5 slow down as the percentage of writes goes up.

The graphs of the two- and four-disk RAID0 arrays have the same shape as the graph of the single drive, indicating that the StorSwitch technology shows excellent results at sorting requests out and sending them to the appropriate hard disk. On the other hand, the three-disk RAID0 behaves somewhat out of the ordinary way when loaded with a lot of reads.

Interestingly, the four-disk RAID0 and RAID10 show very similar speeds in the Random Read mode, and the RAID5 is even a little faster than both of them, although we might have expected to see a small advantage of the RAID10. Probably, the mirror array doesn’t get any advantage from alternating requests between the drives under this type of load.