BiCS FLASH Preview With Toshiba XG5 NVMe SSD

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Conclusion

It's an interesting time for Toshiba. The company is in the midst of a contentious sale of its fab assets. The sale is constantly in the news, and we're not sure how long the name will hang on the fabs. With so much speculation, most of it in the form of intentional leaks (from multiple parties) designed to misguide and increase the bids, we're avoiding reporting every update. Currently there are lawsuits on two continents and a slew of companies stumbling over each other to be the lucky winner. Toshiba chose a preferred buyer, but Sk Hynix partially finances the group. That isn't popular with Western Digital (Toshiba's manufacturing partner) and the government of Japan. Western Digital isn't matters easier by trying to block to sale. Regardless of the outcome, we suspect there will be some hard feelings when it’s all over.

The sale means a lot to enthusiasts, too. The analysts put a lot of weight on Toshiba bringing BiCS NAND to market. It's supposed to the savior of the greatest NAND flash shortage of all time. Toshiba sells flash to half, or more, of the third party SSD vendors. It would be a detriment to the enthusiast market if the fab fell into the hands of a company not willing to share this valuable resource. Apple, Google, and many other bidders could easily use the Toshiba share of the flash flowing from the fab, but Western Digital would still have its share.

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Toshiba XG5 NVMe SSD
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The consumer market has begun the transition to 3-bit per cell flash. There are a handful of MLC products still available for those willing to pay a high price. At least one more big planar MLC announcement is coming in July, but we aren't aware of any more after that from the major players.

That leads us to the Toshiba XG5. As an OEM drive, Toshiba hit a home run. If my next notebook came with this drive in a large enough capacity, I wouldn't replace it. The XG5 is an excellent SSD for what most users do on a notebook or desktop. It's a high performance NVMe drive that even does a good job closing the gap between planar TLC and MLC. It's still not on the same level as the professional workstation products, though.

We're more concerned about some of the latency issues we observed in our testing. The XG5 is still early at this point. The OEMs are busy with validation and will find the same issues. From there, it's just a matter of back and forth with Toshiba to reduce the latency. The drive we examined today is very close to the final XG5 we'll see in systems, but the OCZ RD model will be a little more refined. We'll wait for the retail drive before coming to any conclusions about the future of "high-performance" TLC consumer SSDs.


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Chris Ramseyer
Chris Ramseyer
Chris Ramseyer is a Contributing Editor for Tom's Hardware US. He tests and reviews consumer storage.
9 Comments Comment from the forums
  • Giroro
    There's a lot of words padding out the Features and Specifications page ... but very little meaning or context.
    So flash manufacturers make flash in different die sizes ... is there anything noteworthy about the die sizes in the XG5? Is a 256Gbit die big or small?
    Drive makers tune power consumptions and performance ... ok. Is the XG5 tuned for power or performance. Is the claimed 3,000/2,100 MB/s of sequential read/write particularly high or low compared to other drives?

    What is a "flip chip design"? Is that different than other designs, or is there any particular reasons why a drive should/shouldn't use "flip chip design".

    Most importantly, WTF is BiCS? What aspect of flash is it even trying to improve? Price? Density? Durability?
    Reply
  • mikewinddale
    "There were subtle differences between the OEM XG3 and retail RD400. OCZ tuned the RD400 for enthusiasts and included a custom NVMe driver for Windows. The driver makes a big difference."

    I had problems with the Windows NVME driver on my XG4, so I used the RD400 driver with the XG4, and it worked perfectly, with no problems.

    See https://forums.lenovo.com/t5/ThinkPad-11e-Windows-13-E-and/E570-needs-better-NVMe-driver-support/td-p/3518940?clickid=whh1IG1svXPPQp90UK2rHzHXUkkXJgxNw11DxM0&PID=10451&acid=ww:affiliate:bv0as6&irgwc=1

    and

    https://www.youtube.com/watch?v=3SwvB_drcJE
    Reply
  • irish_adam
    19976663 said:
    There's a lot of words padding out the Features and Specifications page ... but very little meaning or context.
    So flash manufacturers make flash in different die sizes ... is there anything noteworthy about the die sizes in the XG5? Is a 256Gbit die big or small?
    Drive makers tune power consumptions and performance ... ok. Is the XG5 tuned for power or performance. Is the claimed 3,000/2,100 MB/s of sequential read/write particularly high or low compared to other drives?

    What is a "flip chip design"? Is that different than other designs, or is there any particular reasons why a drive should/shouldn't use "flip chip design".

    Most importantly, WTF is BiCS? What aspect of flash is it even trying to improve? Price? Density? Durability?

    There is this great new website called "Google" which has all the answers to your questions.

    I honestly dont mean to be mean, you seem to be lacking in some basic understandings of flash and the flash market which would take someone a little time to explain to you, especially on a forum. You would be far better off just searching for the information yourself, theres plenty of it out there.
    Reply
  • mikewinddale
    19976663 said:
    So flash manufacturers make flash in different die sizes ... is there anything noteworthy about the die sizes in the XG5? Is a 256Gbit die big or small?

    Basically, the smaller the die, the more dies it will take to make an SSD of a given capacity. And more dies means more parallelism, which makes the flash drive faster.

    For example, suppose an SSD is 1 TB. Then it will take twice as many 256 Gbit dies as 512 Gbit dies to make that 1 TB SSD. And more dies means - as I said - more parallelism.

    High-speed SSDs basically rely on internal RAID parallelism. Any given piece of data is read and written to and from multiple dies at once, with the data being split across dies. This way, the SSD can be multiple times faster than any given die.

    Compare a high-speed SSD to a flash thumb drive, for example. Most thumb drives are single-channel and lack a sophisticated controller. While they have lower read latency than mechanical hard drives, because there's no mechanical seek, they are also very slow at sequential operations. A flash thumb drive will have virtually no seek latency, but it also has a peak sequential speed of about 20 MB/s, whereas a mechanical hard drive has a seek latency of about 8 milliseconds, but it can achieve about 500 MB/s in sequential operations.

    So single-channel flash is actually quite slow in some ways. But a high-speed SSD, by splitting data across multiple dies, can increase its speed several-fold. If you write to every die at 20 MB/s, but the data is split across 50 dies, then you might get 1000 MB/s. (These numbers are just illustrative, and I haven't checked them against any actual SSD model.)

    So again, die size matters because the smaller the die, the more dies it takes, and the more parallelism, and the faster the drive.

    For this reason, for any given model of SSD, the larger drives are typically faster. The larger drive has more dies, so more parallelism. Sometimes, the smaller SSD cannot use all of its controller's channels. For example, you might find a 1 TB SSD with an 8 channels controller, and 32 dies, with 4 dies per channel. But the 128 GB model of the same brand, with the same 8 channel controller, might have only 4 dies, only has enough dies to use 4 channels. It's an 8 channel controller, but with only 4 dies, only 4 channels get used, so the 128 GB SSD might be half the speed of the 1 TB SSD. A larger SSD will be more able to utilize multiple channels, and similarly, an SSD with smaller dies will have a larger number of dies, so it will be able to utilize more channels.

    Of course, smaller dies also make it harder to make a large-capacity drive. So there's a tradeoff. In general, dies are getting larger as drives get larger. This means that a brand-new 128 GB SSD today might be slower than one a few years ago, because a few years ago, the dies were smaller, and it took more of them to make a 128 GB SSD. SSDs are generally getting both faster and larger, so if you buy an SSD that is small by today's standards, it will be slower than a larger SSD.

    Reply
  • Giroro
    @MikeWinddale

    That's all good and fine... but once again, a dissertation about the parallelism in flash dies doesn't actually tell me anything at all about the XG5 that is supposedly being previewed.

    Is the drive more parallel than a typical nvme drive, or is it less parallel? Because all the explanation implies that some aspect of this drive's die size and therefore parallelism is noteworthy ... but in what way? Is that supposed to be explaining why this drive has good sequential write speeds? Did the previewer start the test -expecting- those write speeds?
    It's like if you had written 8 paragraphs about why some circuit boards are green and some are blue ... without actually saying what color of circuit board the drive uses. The detail might be interesting, but it doesn't say anything until you give it a point.

    What makes this drive unique? Why is it being previewed? What's the thesis statement to any of this?
    Reply
  • CRamseyer
    The reason why that section is vague is because Toshiba will not tell us. Western Digital / SanDisk will not tell us either. Both companies are fighting like 1st graders on the playground right now. Toshiba just locked WD/SD out of the database files (again) after a judge said they couldn't. There are a few lawsuits on two continents.

    It's my guesstimate that the Toshiba factory is only making 256Gbit die right now on a large scale. That would explain why there is a delay in the 2TB XG5 and 2TB Blue 3D / Ultra 3D. Those capacity sizes would require the larger 512Gbit die with the controller WD/SanDisk used.

    When I wrote the XG5 article I didn't know about the Blue 3D / Ultra 3D 2TB delay. Now I know and can give a better answer to your question.


    So flash manufacturers make flash in different die sizes ... is there anything noteworthy about the die sizes in the XG5? Is a 256Gbit die big or small?

    256Gbit is the small BiCS FLASH die and 512Gbit is the large die. 512Gbit is 64GB. Toshiba has the technology to stack NAND 16 die per package. They are not doing it now with BiCS but it's coming. That means with the 512Gbit die they can make a 1TB package. The package is the black thing on the PCB that hold the NAND, the stuff that holds the data.

    Paired with the right controller Toshiba could put 8 1TB packages in a single SSD and make an 8TB SSD that resembles a consumer SSD. Some companies have very large SSDs already but they use custom controllers that are not "off-the-shelf". The controllers that support (for example) 32 packages are expensive and generate a lot of heat. It's not the sort of thing you want in your desktop or notebook. The new 512Gbit die size will make very high capacity products possible at reasonable price points.

    Companies have used 256Gbit die in the past and Micron has even shipped a 384Gbit die. The odd 384Gbit die caused some other problems but that's not really important in this review other than the experiment was tried and was not as successful as some expected.


    Drive makers tune power consumptions and performance ... ok. Is the XG5 tuned for power or performance. Is the claimed 3,000/2,100 MB/s of sequential read/write particularly high or low compared to other drives?

    The SSD was tuned for both power consumption and performance. On consumer / client SSDs companies choose a balance. Enterprise products generally favor one or the other but most allow users to manually tune the drive to how you want it. For more information look at the Intel DC P3700 user manual or command line guide.

    What is a "flip chip design"? Is that different than other designs, or is there any particular reasons why a drive should/shouldn't use "flip chip design".

    This simply means an exposed chip that doesn't have a shell. Flip chips generally run a few degrees cooler but at the same time are exposed and susceptible to breaking if you put a heatsink on with pressure. The corners are fragile.

    Most importantly, WTF is BiCS? What aspect of flash is it even trying to improve? Price? Density? Durability?

    BiCS FLASH is simple a trademark name for Toshiba's 3D NAND flash. Samsung uses a "special" name too, V-NAND.

    3D NAND gives companies two planes to increase density, horizontal and vertical. Planar (2D) NAND is usually 128Gbit (16GB) so we already see a capacity increase. Using less die to build the same capacity size SSD reduces power consumption. 3D also uses a larger lithography process (the switches inside are farther apart) so that also increases endurance.

    I hope this information helps. I often forget that not everyone is so involved in the technology. I wrote articles that cover topics like these but that was many years ago.
    Reply
  • reghir
    I think you meant "making matters" instead of
    Western Digital isn't matters easier by trying to block to sale.
    Reply
  • SayNO2BS
    How come there is no temperature data? It would be really good to know if this thing runs too not for a 24/7 laptop application.
    Reply
  • aTomek
    What about encryption capabilities? Does it have any (like OPAL)?
    Reply