Quote Originally Posted by One_Hertz View Post
Because 2x X25-V in R0 can not be near 2x faster than a single X25-M. They should be faster, but not 2x, which is absurd.

As soon as I see a large inconsistency like that, the whole benchmark loses validity in my mind.

Edit: to expand, the numbers don't make any sense. Specifically on the heavy trace. A lot of what they do is dependent on sequential writes, which is why we see drives high in that attribute near the top. The X25-M does poorly in comparison to other MLCs that do offer high seq writes, which makes sense. However, the fact that their 80MB/s write speed raid is suddenly 2x faster than a single X25-M which is also 80MB/s makes zero sense whatsoever. The extra read speed of the raid should help, but nowhere near 2x. They either messed something up in this particular benchmark or the whole thing is crap.

Edit2: to expand further, comparing both setups:

Seq read - 370 vs 255
Seq write - 80 vs 80
4kb r write - 60 vs 40
4kb r read - 60 vs 60

The controllers they are using (X25-V and X25-M) are very similar so the speed of reading + writing at once (also very important for the heavy trace, in fact this is why X25-E is the top drive) should be similar.

With that in mind, it does not follow that their trace should spit out 2x higher numbers in favor of the RAID. I would think around 25% higher would be appropriate.
I think he addresses this in his explanation of the benchmark results:

The performance scaling is more than perfect, but that's a side effect of the increase in capacity. Remember that Intel's controller uses any available space on the SSD as spare area to keep write amplification at a minimum. Our storage bench is based on a ~34GB image, which doesn't leave much room for the 40GB X25-V to keep write amplification under control. With two our total capacity is 74.5GB, which is more than enough for this short workload. With the capacity cap removed, the X25-Vs can scale very well. Not nearly twice the performance of an X25-M G2, but much faster than a single drive from Intel