Ok, look, I don't want to argue and you could be right. But - it sounds weird to me. I think that 300-370Mbps is just too low for a PCIe SSD, SanDisk or not. The difference between 128Gb drive and 256Gb can't be 200Mbps, and I know I measured more than ~550Mbps in Blackmagic disk speed test on my friends 13" rMBP (with a 256Gb drive). My Samsung 512Gb SSD in a 15" rMBP easily hits 700Mbps in Blackmagic - so that would mean (since we both have 2013. models with Samsung drives) that your drive is almost twice as slow just because it is 128Gb? While I don't doubt your honesty, this is something hard to believe (as I mentioned, Samsung Pro and Evo drives come in 128, 256, etc. sizes and the speed difference between 128 and 256 is never more than 50Mbps!). Are you sure that your drive is working properly?
Also, if what you say is true, how do you explain the 650Mbps read speed on my FD?
Look, from what I read - and that could be wrong, but it sounds reasonable to me - the SSD part of the Fusion Drive is a standard Apple SSD (that is either SanDisk, Samsung or Toshiba). They use the same PCIe drives across the line, like the 128Gb drives they use in, say, MacBook Airs or 13" Retina MacBook Pros. So, they are not using some different, "slower" drives. Now, these PCIe drives should be fast, hitting anywhere 500-700Mbps depending on the manufacturer. The write speed is slower on the FD because (and I admit, I don't quite understand this technical stuff, I'm just interpreting what I read) the write process is a bit more complex - OS X writes on the SSD for consistency and at the same time moves this data to the HDD for permanent storage, so the result is a bit slower 350-400Mbps. Again, this is just what I read - but it matches my speeds almost to the letter: I have 650Mbps read speed and around 370Mbps write speed on my FD. If I split the two drives, writing on the pure SSD drive should be higher, while the read speeds should be unaffected.
You make a compelling argument, but if what you say is true - shouldn't I have 400Mbps read speeds on my FD (or even less)?
Either way - whether you're right or I'm right doesn't change the fact that - outside benchmarks - using the FD (when it is using the SSD part, which is, honestly, most of the time, and 100% of the time for most used apps and OS) is perceptibly not different than my pure, 512Gb Samsung PCIe SSD, which the fastest drive that Apple currently offers and, as I said, hits 700-750Mbps speeds in all the tests I tried.
So it comes down to this: claiming that some mythical "slower SSDs" are present in FDs is not true. Because when you say something like "Apple is using slower drives for FD" - everyone would naturally assume that they are not using their standard SSD drives but are, in fact, using some cheaper, slower options. Not true. If all the reviews were happy of the new PCIe speed of MacBook Airs that come with 128Gb, then all I'm saying - that's the speed you're getting from a SSD part of a FD drive. Don't scare people off - it's a very, very fast SSD. It is faster than most SSDs you find in PCs these days, it is far from "slow" and, again, the speed of the SSD portion is NOT a reason to avoid FD. Neither is temperature. Get a pure SSD if you want greater reliability and speed consistency. That's it. While the FD is running from a SSD part (again, most of the time) you will not be able to perceive a difference compared to the pure SSD. Even if benchmarks say otherwise.
My problem is that people come here for some honest advice and that this elitist attitude and phrases like "Apple uses slower SSDs" (which is debatable at best) and "FDs generate more heat" and stuff like that may confuse people and drive them off from solutions that would benefit them the most. SSDs are better, but they are NOT the best solution for everyone, as they have a great, cheaper alternative - the Fusion Drive.
/rant off
