The Toshiba XG6 1TB SSD Review: Our First 96-Layer 3D NAND SSD
by Billy Tallis on September 6, 2018 8:15 AM ESTConclusion
The Toshiba XG6 only makes one major change over last year's XG5 by introducing 96-layer 3D NAND, so the product as a whole is mostly an incremental improvement. The XG6 builds upon the XG5 in almost every way with no significant regressions in performance or power efficiency, so it is very easy for OEMs to drop in the XG6 as a replacement for any devices where they are shipping the XG5.
The most significant improvements the XG6 offers over the XG5 show up on some of our more difficult benchmarks, where the XG6 is much faster at mixed random read/write workloads and full-drive performance in general. The XG5 was already a very well-rounded drive with a great combination of performance and power efficiency, and the XG6 only broadens that appeal by shoring up the most significant weaknesses of the XG5. It is rare for a drive to be so free of obvious flaws.
The Toshiba XG5 was the first high-performance NVMe SSD that could match or exceed the power efficiency of most SATA SSDs, meaning that it was no longer necessary to sacrifice battery life to get the improved peak performance of NVMe. Since then, some of the power efficiency records have been beaten by TLC-based NVMe SSDs with newer controllers. The WD Black did the most to raise the bar for power efficiency, but some of the entry-level NVMe alternatives that have appeared are also quite a bit more efficient that the typical high-end drive. The Toshiba XG6 either retakes the lead or comes close enough to effectively tie the competition in every one of our power efficiency measurements.
The only significant downside to the Toshiba XG6 is that it never really improves upon Toshiba's performance enough to set records; it cannot match the peak performance offered by some of the top consumer NVMe drives currently on the market. Toshiba would have a hard time selling the XG6 as a retail product for enthusiasts who are seeking the bragging rights of the fastest storage money can buy. But the XG6 is an OEM drive and performs well enough to give any notebook a credible claim to offering high-end storage. If your next notebook purchase includes an XG6, there would be absolutely no need to upgrade it with any current retail SSD unless a 2TB drive was needed. The WD Black is the only drive that could offer better performance without sacrificing battery life, and it can't beat the XG6 across the board due to its subpar sequential read performance. (The WD Black's OEM counterpart WD SN720 is probably the most direct competition to the XG6, but I suspect the XG6 will offer lower costs to OEMs.)
If Toshiba can ramp up output of their 96L 3D TLC NAND quickly, I would like to see a retail version of the XG6. With a bit more firmware tweaking to improve peak performance, Toshiba could probably have a very cost-effective drive that would compete well against the cheapest 8-channel NVMe SSDs and remove the need for the DRAMless RC100 to serve as their low-cost NVMe drive. For the retail market where desktops play a much bigger role than in the OEM market, it would be appropriate to sacrifice some of their excess power efficiency to deliver higher performance, if their controller makes that possible. But if Toshiba isn't prepared to compete in that mid-level price range, they should wait until they have a faster controller to pair with their 96L NAND to match the peak performance numbers we are seeing from Silicon Motion, Western Digital and Samsung.
Without retail pricing it is difficult to judge the cost effectiveness of the XG6, but the 96L NAND should help Toshiba offer OEMs a bargain. There's no reason for OEMs to shy away from using the XG6 in their systems, and no reason for consumers to be disappointed if they find the XG6 inside their new system purchase.
As an aside, I'm strongly considering putting the XG6 into my personal laptop for a while. It's an older machine that only has a PCIe 2.0 link to the SSD so none of the XG6's performance deficiencies relative to the fastest drives on the market will make much difference, and the XG6 will probably offer the best battery life of any drive I have on hand.
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Spoelie - Thursday, September 6, 2018 - link
2 short questions:- what happened to the plextor M9Pe, performance is hugely different from the review back in march.
- i know this is already the case for a year or so, but what happened to the perf consistency graphs, where can i deduce the same information from?
hyno111 - Thursday, September 6, 2018 - link
M9Pe had firmware updates, not sure if it's applied or related though.DanNeely - Thursday, September 6, 2018 - link
I don't recall the details, but something went wrong with generating the performance consistency data, and they were pulled pending finding a fix due to concerns they were no longer valid. IF you have the patience to dig through the archive, IIRC the situation was explained in the first review without them.Billy Tallis - Thursday, September 6, 2018 - link
I think both of those are a result of me switching to a new version of the test suite at the same time that I applied the Spectre/Meltdown patches and re-tested everything. The Windows and Linux installations were updated, and a few tweaks were made to the synthetic test configuration (such as separating the sequential read results according to whether the test data was written sequentially or randomly). I also applied all the drive firmware updates I could find in the April-May timeframe.The steady-state random write test as it existed a few years ago is gone for good, because it really doesn't say anything relevant about drives that use SLC caching, which is now basically every consumer SSD (except Optane and Samsung MLC drives). I also wasn't too happy with the standard deviation-based consistency metric, because I don't think a drive should be penalized for occasionally being much faster than normal, only much slower than normal.
To judge performance consistency, I prefer to look at the 99th percentile latencies for the ATSB real-world workload traces. Those tend to clearly identify which drives are subject to stuttering performance under load, without exaggerating things as much as an hour-long steady-state torture test.
I may eventually introduce some more QoS measures for the synthetic tests, but at the moment most of them aren't set up to produce meaningful latency statistics. (Testing at a fixed queue depth leads to the coordinated omission problem, potentially drastically understating the severity of things like garbage collection pauses.) At some point I'll also start graphing the performance as a drive is filled, but with the intention of observing things like SLC cache sizes, not for the sake of seeing how the drive behaves when you keep torturing it after it's full.
I will be testing a few consumer SSDs for one of my upcoming enterprise SSD reviews, and that will include steady-state full drive performance for every test.
svan1971 - Thursday, September 6, 2018 - link
I wish current reviews would use current hardware, the 970 Pro replaced the 960 Pro months ago.Billy Tallis - Thursday, September 6, 2018 - link
I've had trouble getting a sample of that one; Samsung's consumer SSD sampling has been very erratic this year. But the 970 Pro is definitely a different class of product from a mainstream TLC-based drive like the XG6. I would only include 970 Pro results here for the same reason that I include Optane results. They're both products for people who don't really care about price at all. There's no sensible reason to be considering a 970 Pro and an XG6-like retail drive as both potential choices for the same purchasing decision.mapesdhs - Thursday, September 6, 2018 - link
Please never stop including older models, the comparisons are always useful. Kinda wish the 950 Pro was in there too.Spunjji - Friday, September 7, 2018 - link
I second this. I know that I am (and feel most other savvy consumers would be) more likely to compare an older high-end product to a newer mid-range product, partly to see if it's worth buying the older gear at a discount and partly to see when there is no performance trade-off in dropping a cost tier.jajig - Friday, September 7, 2018 - link
I third it. I want to know if an upgrade is worth while.dave_the_nerd - Sunday, September 9, 2018 - link
Very much this. And not all of us upgrade our gear every year or two.