What Micron's Upcoming 3D NAND Means for SSD Capacity, Performance, and Cost

Subject: Storage | February 14, 2016 - 07:51 PM |
Tagged: vnand, ssd, Samsung, nand, micron, Intel, imft, 768Gb, 512GB, 3d nand, 384Gb, 32 Layer, 256GB

You may have seen a wave of Micron 3D NAND news posts these past few days, and while many are repeating the 11-month old news with talks of 10TB/3.5TB on a 2.5"/M.2 form factor SSDs, I'm here to dive into the bigger implications of what the upcoming (and future) generation of Intel / Micron flash will mean for SSD performance and pricing.

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Remember that with the way these capacity increases are going, the only way to get a high performance and high capacity SSD on-the-cheap in the future will be to actually get those higher capacity models. With such a large per-die capacity, smaller SSDs (like 128GB / 256GB) will suffer significantly slower write speeds. Taking this upcoming Micron flash as an example, a 128GB SSD will contain only four flash memory dies, and as I wrote about back in 2014, such an SSD would likely see HDD-level sequential write speeds of 160MB/sec. Other SSD manufacturers already recognize this issue and are taking steps to correct it. At Storage Visions 2016, Samsung briefed me on the upcoming SSD 750 Series that will use planar 16nm NAND to produce 120GB and 250GB capacities. The smaller die capacities of these models will enable respectable write performance and will also enable them to discontinue their 120GB 850 EVO as they transition that line to higher capacity 48-layer VNAND. Getting back to this Micron announcement, we have some new info that bears analysis, and that pertains to the now announced page and block size:

  • 256Gb MLC: 16KB Page / 16MB Block / 1024 Pages per Block

  • 384Gb TLC: 16KB Page / 24MB Block / 1536 Pages per Block

To understand what these numbers mean, using the MLC line above, imagine a 16MB CD-RW (Block) that can write 1024 individual 16KB 'sessions' (Page). Each 16KB can be added individually over time, and just like how files on a CD-RW could be modified by writing a new copy in the remaining space, flash can do so by writing a new Page and ignoring the out of date copy. Where the rub comes in is when that CD-RW (Block) is completely full. The process at this point is very similar actually, in that the Block must be completely emptied before the erase command (which wipes the entire Block) is issued. The data has to go somewhere, which typically means writing to empty blocks elsewhere on the SSD (and in worst case scenarios, those too may need clearing before that is possible), and this moving and erasing takes time for the die to accomplish. Just like how wiping a CD-RW took a much longer than writing a single file to it, erasing a Block takes typically 3-4x as much time as it does to program a page.

With that explained, of significance here are the growing page and block sizes in this higher capacity flash. Modern OS file systems have a minimum bulk access size of 4KB, and Windows versions since Vista align their partitions by rounding up to the next 2MB increment from the start of the disk. These changes are what enabled HDDs to transition to Advanced Format, which made data storage more efficient by bringing the increment up from the 512 Byte sector up to 4KB. While most storage devices still use 512B addressing, it is assumed that 4KB should be the minimum random access seen most of the time. Wrapping this all together, the Page size (minimum read or write) is 16KB for this new flash, and that is 4x the accepted 4KB minimum OS transfer size. This means that power users heavy on their page file, or running VMs, or any other random-write-heavy operations being performed over time will have a more amplified effect of wear of this flash. That additional shuffling of data that must take place for each 4KB write translates to lower host random write speeds when compared to lower capacity flash that has smaller Page sizes closer to that 4KB figure.

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A rendition of 3D IMFT Floating Gate flash, with inset pulling back some of the tunnel oxide layer to show the location of the floating gate. Pic courtesy Schiltron.

Fortunately for Micron, their choice to carry Floating Gate technology into their 3D flash has netted them some impressive endurance benefits over competing Charge Trap Flash. One such benefit is a claimed 30,000 P/E (Program / Erase) cycle endurance rating. Planar NAND had dropped to the 3,000 range at its lowest shrinks, mainly because there was such a small channel which could only store so few electrons, amplifying the (negative) effects of electron leakage. Even back in the 50nm days, MLC ran at ~10,000 cycle endurance, so 30,000 is no small feat here. The key is that by using that same Floating Gate tech so good at controlling leakage for planar NAND on a new 3D channel that can store way more electrons enables excellent endurance that may actually exceed Samsung's Charge Trap Flash equipped 3D VNAND. This should effectively negate the endurance hit on the larger Page sizes discussed above, but the potential small random write performance hit still stands, with a possible remedy being to crank up the Over-Provisioning of SSDs (AKA throwing flash at the problem). Higher OP means less active pages per block and a reduction in the data shuffling forced by smaller writes.

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A 25nm flash memory die. Note the support logic (CMOS) along the upper left edge.

One final thing helping out Micron here is that their Floating Gate design also enables a shift of 75% of the CMOS circuitry to a layer *underneath* the flash storage array. This logic is typically part of what you see 'off to the side' of a flash memory die. Layering CMOS logic in such a way is likely thanks to Intel's partnership and CPU development knowledge. Moving this support circuitry to the bottom layer of the die makes for less area per die dedicated to non-storage, more dies per wafer, and ultimately lower cost per chip/GB.

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Samsung's Charge Trap Flash, shown in both planar and 3D VNAND forms.

One final thing before we go. If we know anything about how the Intel / Micron duo function, it is that once they get that freight train rolling, it leads to relatively rapid advances. In this case, the changeover to 3D has taken them a while to perfect, but once production gains steam, we can expect to see some *big* advances. Since Samsung launched their 3D VNAND their gains have been mostly iterative in nature (24, 32, and most recently 48). I'm not yet at liberty to say how the second generation of IMFT 3D NAND will achieve it, but I can say that it appears the next iteration after this 32-layer 256Gb (MLC) /384Gb (TLC) per die will *double* to 512Gb/768Gb (you are free to do the math on what that means for layer count). Remember back in the day where Intel launched new SSDs at a fraction of the cost/GB of the previous generation? That might just be happening again within the next year or two.

Samsung Launches 950 PRO - 300,000 IOPS and 2.5 GB/sec from a M.2 V-NAND SSD!

Subject: Storage | September 22, 2015 - 06:39 AM |
Tagged: vnand, V-NAND, ssd, Samsung, pcie, NVMe, M.2 2280, M.2, 950 PRO, 512GB, 256GB

I’ve been waiting a long time for Samsung to put their V-NAND flash memory into a PCIe connected SSD, and such a product has just been officially announced at the Samsung SSD Global Summit.

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Samsung’s new product launching will be called the 950 PRO. This will be an M.2 2280 form factor product running at PCIe 3.0 x4. Equipped with Samsung’s 32-layer V-NAND and using the NVMe protocol enabled by a new UBX controller, the 950 PRO will be capable of up to an impressive 300,000 random read IOPS. Random writes come in at 110,000 IOPS and sequential throughputs are expected to be 2.5 GB/sec reads and 1.5 GB/sec for writes. Available capacities will be 256GB and 512GB.

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Pricing:

The 950 PRO will be shipping with a 5-year warranty rated at 200 terabytes written for the 256GB model and 400 TBW for the 512GB. That works out to just over 100GB per day for both capacities.

These hit retail in October and we currently have samples in hand for testing.

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(for those curious, both capacities only have components on the front side of the PCB)

Full press blast after the break.

Source: Samsung
Subject: Storage
Manufacturer: Plextor
Tagged: ssd, plextor, pcie, 256GB

Introduction, Specifications and Packaging

Introduction:

Plextor launched their M6e PCIe SSD in mid-2014. This was the first consumer retail available native PCIe SSD. While previous solutions such as the OCZ RevoDrive bridged SATA SSD controllers to PCIe through a RAID or VCA device, the M6e went with a Marvell controller that could speak directly to the host system over a PCIe 2.0 x2 link. Since M.2 was not widely available at launch time, Plextor also made the M6e available with a half-height PCIe interposer, making for a painless upgrade for those on older non M.2 motherboards (which at that time was the vast majority).

With the M6e out for only a few months time (and in multiple versions), I was surprised to see Plextor launch an additonal version of it at the 2015 CES this past January. Announced alongside the upcoming M7e, the M6e Black Edition is essentially a pimped out version of the original M6e PCIe:

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We left CES with a sample of the M6e Black, but had to divert our attention to a few other pressing issues shortly after. With all of that behind us, it's time to get back to cranking out the storage goodness, so let's get to it!

Read on for the full review!

The Corsair Neutron Series XT could be a mid-range contender, depending on the price

Subject: Storage | November 24, 2014 - 09:35 PM |
Tagged: ssd, sata, PS3110-S10, phison, Neutron XT, corsair, 256GB

Allyn recently reviewed the Corsair Neutron Series XT but as it is a brand new controller it is always worth a second opinion.  The Tech Report also recently tested this SSD, with its four core PS3110 controller and A19 variant of Toshiba's 19-nm MLC NAND.  Three of those cores are devoted to behind the scenes tasks such as garbage collection which should help performance when the drive starts to approach full capacity.  When testing performance they did see improvements from the first Phison controlled drive, the Force Series LS which sits at the bottom of their performance ranking.  That was not all that held back this drive, lack of support for features which have become common such as Microsoft eDrive put this drive behind the top competition and if Corsair is to make this drive a contender they are going to have to think very carefully about what the MSRP will be.

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"Corsair's new Neutron Series XT pairs a quad-core Phison controller with Toshiba's latest MLC NAND. We've taken the 240GB version for a spin to see if it can hang with the big boys."

Here are some more Storage reviews from around the web:

Storage

Subject: Storage
Manufacturer: Plextor
Tagged: ssd, plextor, pcie, 256GB

Introduction, Specifications and Packaging

Introduction:

In recent years, Plextor has branched beyond their renowned lines of optical storage devices, and into the realm of SSDs. They have done fairly well so far, treading carefully on their selection of controllers and form factors. Their most recent offerings include the M6S and M6M (reviewed here), and are based on Marvell controllers coupled with Toshiba flash. Given that the most recent Marvell controllers are also available in a PCIe variant, Plextor also chose to offer their M6 series in PCIe half height and M.2 form factor. These last two offerings are not simply SATA SSDs bridged over to PCIe, they are natively PCIe 2.0 x2 (1 GB/s), which gives a nice boost over the current SATA limit of 6Gb/sec (600 MB/sec). Today we are going to kill two birds with one stone by evaluating the half-height PCIe version:

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As you can see, this is nothing more than the M.2 version on a Plextor branded interposer board. All results of this review should be identical to the bare M.2 unit plugged into a PCIe 2.0 x2 capable M.2 port on either a motherboard or mobile device. Note that those devices need to support the 2280 form factor, which is 80mm in length.

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Here's the M.2 version installed on an ASUS X99-Deluxe, as tested by Morry.

Read on for the full review!

Subject: Storage
Manufacturer: Corsair

Introduction, Specifications and Packaging

Introduction:

During our coverage of the Flash Memory Summit, we spotted the new Phison PS3110-S10 controller:

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At that time we only knew that Phison was going to team up with another SSD manufacturer to get these to market. We now know that manufacturer is Corsair, and their new product is to be called the Neutron XT. How do we know this? Well, we've got one sitting right here:

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While the Neutron has not officially launched (pricing is not even available), we have been afforded an early look into the performance of this new controller / SSD. While this is suspected to be a cost effective entry into the SSD marketplace, for now all we can do is evaluate the performance, so let's get to it!

Read on for the full review!

Subject: Storage
Manufacturer: Samsung

Introduction

Given that we are anticipating a launch of the Samsung 850 EVO very shortly, it is a good time to back fill on the complete performance picture of the 850 Pro series. We have done several full capacity roundups of various SSD models over the past months, and the common theme with all of them is that as the die count is reduced in lower capacity models, so is the parallelism that can be achieved. This effect varies based on what type of flash memory die is used, but the end result is mostly an apparent reduction in write performance. Fueling this issue is the increase in flash memory die capacity over time.

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There are two different ways to counteract the effects of write speed reductions caused by larger capacity / fewer dies:

  • Reduce die capacity.
  • Increase write performance per die.

Recently there has been a trend towards *lower* capacity dies. Micron makes their 16nm flash in both 128Gbit and 64Gbit. Shifting back towards the 64Gbit dies in lower capacity SSD models helps them keep the die count up, increasing overall parallelism, and therefore keeping write speeds and random IO performance relatively high.

Read on for the results of our full capacity roundup!

Subject: Storage
Manufacturer: ADATA

Introduction, Specifications and Packaging

Introduction:

It seems a lot of folks have been incorporating Silicon Motion's SM2246EN controller into their product lines. We first reviewed the Angelbird SSD wrk, but only in a 512GB capacity. We then reviewed a pair of Corsair Force LX's (256GB and 512GB). ADATA has joined the club with their new Premier SP610 product line, and today we are going to take a look at all available capacities of this new model:

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It's fortunate that ADATA was able to sample us a full capacity spread, as this will let us evaluate all shipping SSD capacites that exist for the Silicon Motion SM2246EN controller.

Continue reading as we evaluate the ADATA Premier SP610!

Subject: Storage
Manufacturer: Corsair

Introduction, Specifications and Packaging

Introduction:

We first looked at the Silicon Motion 2246EN controller in our Angelbird SSD wrk review. In that review, we noted the highest sequential performance seen in any SATA SSD reviewed to date. Eager to expand our testing to include additional vendors and capacities, our next review touching on this controller is the Corsair Force LX series of SSDs. The Force LX Series is available in 128GB, 256GB, and 512GB capacities, and today we will look at the 256GB and 512GB iterations of this line:

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Continue reading as we evaluate the Corsair Force LX series:

Subject: Storage
Manufacturer:

Introduction, Specifications and Packaging

Introduction:

A few months back, we took a look at the ADATA Premier Pro SP920 series of SSDs. Those came equipped with the Marvell 88SS9189 controller. Marvell SSD controllers have always done a good job, and they were among the first to support SATA 6Gbit speeds. Crucial was one of the first to adopt the Marvell controller into their SATA SSD products, so it seems fitting that we revisit the 88SS9189 controller in the form of Micron's Crucial M550 Series of SSDs:

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Being one of the big manufacturers of SSDs, Micron has some cool production videos. Here's one of their videos covering the production of flash all the way through to the assembly of an SSD. We actually toured one of these plants a few years back. Good stuff:

Continue reading as we evaluate all available capacities of the Crucial M550!!