Silicon Motion SM2256 SSD Controller Preview: TLC for Everyone
by Kristian Vättö on June 17, 2015 8:15 AM EST- Posted in
- Storage
- SSDs
- TLC
- Silicon Motion
- SM2256
Final Words
To get the elephant in the room out first, I'm not overly satisfied with the performance. The SM2256 is slower than the other TLC SSDs (850 EVO & Ultra II) on the market and not just by an insignificant margin. Especially small size random IOs are rather slow, which impact the overall performance because many IOs in client workloads are 4KB and random in nature. For very light IO workloads that obviously won't be a major issue, but anything more IO intensive (like virtualization) could be severely impacted by SM2256's high latency. To be frank, I never expected the SM2256 to perform like the SM2246EN because no controller can get around the performance limitations of TLC NAND, but given how well the SM2246EN performs I was expecting the SM2256 to be faster than it is.
Aside from performance, the other problem with SM2256 is its power consumption. The part I absolutely love in the SM2246EN is its extremely low power consumption, but the SM2256 practically doubles the power draw that makes it one of the least efficient drives we have tested. Again, expecting the SM2256 to be as efficient as the SM2246EN wouldn't be fair because TLC inherently has higher power consumption as it needs a higher number of program-verify iterations, but even then doubled power consumption is a bit more than I was looking forward to.
I do wonder how big of a difference the NAND makes, though. As I mentioned on page one, we will likely never see this configuration on the retail market because Samsung doesn't sell its TLC to third parties in large quantities, so I'm not sure if Silicon Motion has spent a ton of resources in optimizing the firmware for NAND that won't be used outside of engineering samples. I certainly hope that the SM2256 performs better with NAND from other vendors because as it stands the performance is quite underwhelming against the competition, but nothing that couldn't be fixed with better optimization. After all, the sample I have doesn't have the final retail firmware in it, so we will have to wait for shipping drives before drawing the final verdict on the SM2256.
In any case, it will all boil down to pricing anyway. If Silicon Motion's OEM partners can drive the prices down with the SM2256, I will be totally fine with the performance because the SM2256 is still more than fine for basic usage. TLC SSD pricing was actually one of the things I was very vocal about at Computex because OEMs can't price their TLC drives similarly to the MLC ones and expect it to be a good sale. TLC isn't as good as MLC and that's a fact that nobody can deny. Especially after Samsung's issues with TLC the market has become more skeptical about TLC in general, so saving a few bucks isn't enough anymore for the educated buyers to choose TLC over MLC -- I think the difference has to be in the order of 10% or so to be worth the lower performance and possible long-term reliability risks that TLC brings. I do believe that the SM2256 is a vehicle capable of delivering such cost savings, but for now we will just need to wait and see what happens.
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watzupken - Wednesday, June 17, 2015 - link
Looking at the state of the Samsung 840, I am still not convinced with TLC based SSDs. With value in mind, SSD is also walking down the path of cheap but unreliable storage solutions from my opinion. E.g. mechanical drives used to last a very long time, but not now even though they are cheap.leexgx - Saturday, June 20, 2015 - link
the problem with 840 and 840 evo is just that its not refreshing the cells when it should be (the data is still retained even if its slow doing it) SSDs problem with retaining data is an issue towards end of life but that happens on all SSDs (more a concern for commercial use then consumer drives)der - Wednesday, June 17, 2015 - link
Wow great!RU482 - Wednesday, June 17, 2015 - link
IS THAT....A HAIR?i7 - Wednesday, June 17, 2015 - link
Looks like it to me.KAlmquist - Wednesday, June 17, 2015 - link
"OEMs can't price their TLC drives similarly to the MLC ones and expect it to be a good sale."Agreed. If you look at the prices of Samsung's 850 series, it's around $0.90 per GB of nand cells plus a fixed cost of $30. So you can get an MLC model for better performance at $0.45/GB of capacity, or a TLC model with lower performance at $0.30/GB of capacity. If that type of pricing is adopted by other SSD manufacturers, then TLC becomes very tempting; otherwise not so much.
The other thing about the 850 line is that the relatively large cell size associated with 3D Nand appears to have eliminated the problem with data deterioration that we saw on the 840 EVO. So TLC will become more attractive next year when 3D Nand becomes available from other manufacturers.
nwarawa - Wednesday, June 17, 2015 - link
10% my tush. Try 20%+. Considering I can get a good MLC 256GB-class drive like a BX100 right now for around $100, if they can't get a similar TLC drive under $80, I won't even give it a second glace.revanchrist - Wednesday, June 17, 2015 - link
TLC is going to be real cheap. Tigo, a Chinese 3rd-party ssd manufacturer has announced its tlc ssd based on Silicon Motion controller and SK Hynix nand chips last week, available in quantity up to 2TB. They've only disclosed the price of the 240gb model, which is RMB 399, roughly 65 USD. FFS that could translate to 260 USD for a 1TB model OMG.revanchrist - Wednesday, June 17, 2015 - link
The controller is exactly SM2256 and the nand is 16nm 128Gb TLC from SK Hynix.anactoraaron - Wednesday, June 17, 2015 - link
OFF TOPIC: Wow you guys must have had some serious issues with the LG G4 for it to be 2+ weeks past release and still no review.I'm guessing you were about to publish the issues you have had with the device (missed taps/unresponsive screen, slow charging/heat, lag/stutter, etc) and basically not recommend anyone purchase it and you were 'advised' by LG to not publish this until they have had a chance to fix those issues, which according to Android Central will be in the next 3-4 weeks. I just can't recall a review of a flagship device that wasn't out within 2 weeks of release (unless it was a Sony device since they won't comp anything to you guys to review).
I don't see the point of waiting, because even with the issues I personally have (unresponsive screen/lag/stutter) the G4 is still a solid device.
This isn't a knock on you guys - you do probably the most unbiased and thorough reviews. The delay on this review is just starting to smell a bit to me.