What's TLC is SLC Again: MEMXPRO Introduces PC32 Full-Drive Pseudo-SLC SSDsby Anton Shilov on February 21, 2020 12:00 PM EST
Pseudo-SLC caches for TLC-based SSDs are almost as old as TLC NAND itself, serving as a simple and practical solution to TLC's lower sustained throughput. But like all caches, pseudo-SLC caches have a finite size; and once you run over it, you're back to directly hitting the TLC. So what is a user or system builder to do if they need a drive with SLC-like performance all the time? For a while, the answer to that has been MLC drives, but with MLC slowly but surely on its way out as well, other solutions are needed. And to that end, MEMXPRO is introducing a series of new drives that go the opposite direction, embracing pseudo-SLC mode to its very core by making the entire drive pseudo-SLC.
Based on 64-layer 3D TLC memory, MEMXPRO's PC32 drives use drive-wide pseudo-SLC mode to give the drives MLC-like performance and reliability. This setup is overkill for most applications, but for use cases that require SSDs with long lifespans, and high durability – MEMXPRO's specialty – the PC32 fills an important niche.
The MEMXPRO PC32 drives in are based on the Silicon Motion SM2262EN controller as well as Micron’s B17A 64-layer 3D TLC NAND memory, which is rated for 10,000 P/E cycles. By putting the drives in pseudo-SLC mode, the manufacturer is able to increase their durability to 40,000 P/E cycles, albeit at the cost of capacity. Since TLC NAND that offers 3-bits of storage per cell is otherwise reduced to 1-bit per cell, the drives are available in capacities from just 80 GB to 320 GB. As for throughput, with the high-end controller used for the drive, MEMXPRO has rated the drives' sustained sequential read and write performance 3,250 and 2,980 MB/s respectively, which is in line with other modern SSDs featuring a PCIe 3.0 x4 interface.
Under the hood, MEMXPRO’s PC32 drives are built on PCBs with side fill and under fill protective conformal coating to enhance their reliability. Also, they are designed to ensure reliable performance within industrial temperature ranges (-40°C to +85°C), so the number of applications they can address is wide. Meanwhile, the SM2262EN controller fully supports AES 256-bit encryption with TCG OPAL 2.0 compliance, so the manufacturer can enable this functionality at request with an appropriate firmware. PC32 also supports MEMXPRO’s proprietary mSMART intelligent storage management tool to monitor drive health and lifespan status that warns owner of the drive about increased risks.
MEMXPRO will demonstrate its PC32 and other SSDs at the upcoming Embedded World 2020 trade show later this month, and will start taking orders on the drives shortly. The company has also noted their interest in developing more all-SLC drives, noting that that if the market requires higher-capacity products in a different form-factor, those SSDs could be developed as well.
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Supercell99 - Friday, February 21, 2020 - linkWhy don't they just make SLC drives again? Why did they stop? Capacity ?
timbotim - Friday, February 21, 2020 - linkThe consumer PC market is generally driven by cost to the consumer. Once a technology becomes slightly cheaper to produce (and thus sell), economies of scale drive the cost to consumers even lower, to the point where a superior but less economic technology eventually bites the dust. Also bear in mind that manufacturers are driven by *total* profits, they have little incentive to maintain a product which is individually lucrative (say 90% profit) when they can sell 1000x as many parts at 1%.
Enterprise market is different however. Cost as a parameter vies with reliability, etc.
You can still buy (Enterprise) SLC drives at about $5 per GB. But to be fair, at that price, consumers would be looking at Optane I would imagine.
nandnandnand - Friday, February 21, 2020 - linkDepending on the pricing, 3D XPoint could soundly beat this.
Billy Tallis - Friday, February 21, 2020 - linkCost for the 320GB SLC should be similar to a 1TB TLC drive, which is ~$150 at retail plus the mark-up for industrial grade rather than consumer grade. The Intel Optane 800P was $199 for 118GB, and was only faster for random reads.
hammer256 - Friday, February 21, 2020 - linkSo 905p at 480GB is about $600, which is $1.25/GB. If this drive is $150 for a 320GB, thats $0.46/GB. And if it sells for $200, then it's $0.625/GB. So Optane ends up been between 2-2.6X more expensive per GB. But, you get way better and consistent random read and write IO, and no write amplification to worry about, so maybe similar endurance. So depending on your workload, I can definitely see a case for paying more for Optane, e.g., databases.
Billy Tallis - Friday, February 21, 2020 - linkIf you have a workload with really heavy sustained random writes, or if you need super low random read latency, then Optane's performance could be advantageous. But this isn't a Z-NAND or XL-Flash drive that's trying to compete in that space. It's a drive for embedded and industrial use cases where you want to keep it in service for way longer than 5 years.
Soulkeeper - Saturday, February 22, 2020 - linkThe SSDs are getting more complex. I wouldn't be surprised if the newer controllers start having 8+ cores to deal with the complex algorithms involved in the multi tiered read/write schemes that seem to be needed now. NVME host side cache -> SSD DRAM cache -> 8x+ nand (slc -> tlc -> qlc). They are going to have a hard time saturating pcie 5.0/6.0 with these slower qlc/tlc solutions. Time to get clever.
mode_13h - Saturday, February 22, 2020 - linkActually, it's going the other direction. Enterprise SSDs are starting to expose the raw flash, and just let the host CPU do all of the management. I forget what the standard is called...
FunBunny2 - Sunday, February 23, 2020 - link"I forget what the standard is called..."
oddly, in a comment further above, you say that the NAND array is supported, in situ, by circuitry (hardwired logic?) to handle R/W to TLC & QLC? it's always seemed most logical (hehe) to me that the controller is the best place to put that control. neither the NAND nor cpu. after all, the signal send to the NAND array is already at the value/voltage of the multi-bit value. why would the NAND array need to do any more with the value than simple SLC? just get/set the cell? a link would suffice. anyone actually know?
mode_13h - Wednesday, February 26, 2020 - linkYou need to do wear-leveling, ECC, bad block relocation, and potentially managing pseudo-SLC buffering. A lot of that can be done at the filesystem level. Putting that level of control in the host CPU can avoid some redundancy, improve QoS, and perhaps benefit energy efficiency.