Let's try something a little different. Instead of searching for performance, let's see what a properly redundant array is capable of.
With a two disk RAID 1 array, ATTO shows us:
We see here the result of having to write everything twice - a 10% "write penalty" on the array. Instead of achieving 105MBps as we do for reads, we see a maximum of 95MBps for writes. Let’s see what HDTach has to say about the mirror set:
Pretty good results for a mirror set. Unlike the RAID 0 set, we see a traditional performance curve, starting high and gradually worsening (as the heads move towards the centre of the disk). We don't see the same read performance as the RAID 0 set though, which indicates that the embedded RAID controller is not capable of using both disks simultaneously to satisfy read requests. Perhaps what we see is more a symptom of a lack of Command Queuing (NCQ) which significantly improves performance in multiple-disk arrays. On to HDTune then, to see the difference between sequential and random access:
An average of 85MBps across the array is quite reasonable and matches reasonably closely the performance of a single disk. We match the sequential performance curve from HDTach and also shows the same improvement from the very start of the disk towards the middle.
Random IO still shows no change - perhaps another indication that the FiT cannot effectively use more than 1 disk at once. Don't confuse the scale on this graph with that of the RAID 0 graph - the RAID 0 graph has an outlier - a single 4KB IO that required 80ms to complete and thus changed the vertical scale. The random IO performance is comparable, between the two arrays.
