Original Link: https://www.anandtech.com/show/13254/the-toshiba-xg6-1tb-ssd-review-first-96l-3d-nand
The Toshiba XG6 1TB SSD Review: Our First 96-Layer 3D NAND SSD
by Billy Tallis on September 6, 2018 8:15 AM ESTIn 2017, Toshiba was the first vendor to ship 64-layer 3D NAND in the consumer SSD market with their XG5 NVMe SSD. Now a little over a year later, the XG6 is the first SSD with 96-layer 3D NAND. The new generation of flash memory allows for better performance, improved power efficiency, and lower costs.
As the high-end tier of Toshiba's OEM SSD product line, the XG series is not officially available for retail purchase, but we think this one is pretty likely to be used as the starting point for a retail product. The last XG series drive with a retail counterpart was the XG3, the planar MLC-based sibling to the OCZ RD400. Toshiba's low-end NVMe BG series of single-chip BGA SSDs also got a retail version in the Toshiba RC100, mounted on a M.2 2242 card. Retail and OEM versions usually have some firmware differences and occasionally one or two significant hardware differences such as 19nm vs 15nm MLC for the XG3 and RD400, or 30mm vs 42mm card length for the BG3 and RC100. Despite those differences, OEM SSDs are usually a pretty accurate preview of later retail versions.
OEM SSDs are usually not designed with maximum performance as the primary goal. OEMs prefer to have the option of sourcing more than one SSD for use in each of their systems, and they aren't interested in paying a large premium for some of their drives to be substantially faster than the rest. That said, for certain systems OEMs do want a true high-end drive, and the bar for that gets higher with every generation. Late last year, Toshiba introduced a higher performing XG5-P variant with a focus on better performance for more intensive workloads and benchmarks that exercise the full drive capacity with lots of random access. The XG6 is only intended to directly replace the XG5, but in light of the performance increases it brings, the 1TB XG5-P is now obsolete. The 2TB XG5-P may stick around for a while longer simply because the XG6 is not available in capacities above 1TB.
The new 96-layer BiCS4 3D TLC NAND used by the Toshiba XG6 is the most advanced flash memory currently shipping, but relative to the 64-layer BiCS3 that currently makes up most of the NAND volume from Toshiba and SanDisk it is more of an incremental update rather than revolutionary change. The increased layer count improves density but the TLC die capacities are still 256Gb and 512Gb. The I/O interface has been upgraded to the Toggle NAND 3.0 standard, with speeds in the 667-800MT/s range compared to the 400-533MT/s speeds used by earlier 3D NAND from Toshiba. The speed bump brings Toshiba's NAND up to par for its current competition, but it will soon be eclipsed by the 1.4GT/s Toggle 4.0 interface that Samsung's upcoming 96L V-NAND will be using. (Though it remains to be seen whether such a big increase in interface speed will have much effect on overall drive performance when drives will still be limited to PCIe 3.0 x4 speeds for another generation or two.) The NAND interface voltage has also dropped from 1.8V to 1.2V, so the higher I/O speed shouldn't have much impact on power efficiency.
Toshiba OEM NVMe SSD Comparison | ||||||
Model | XG6 | XG5 | XG5-P | BG3 | XG3 | |
Retail Counterpart | None | RC100 | RD400 | |||
Capacities | 256GB, 512GB, 1024GB | 1TB, 2TB | 128GB, 256GB, 512GB | 128GB, 256GB, 512GB, 1024GB | ||
Form Factor | M.2 2280 | M.2 2230 | M.2 2280 | |||
Host Interface | PCIe 3.1 x4 | PCIe 3.1 x2 | PCIe 3.1 x4 | |||
Protocol | NVMe 1.3a | NVMe 1.2.1 | NVMe 1.1b | |||
NAND Flash | Toshiba 96L BiCS4 3D TLC | Toshiba 64L BiCS3 3D TLC | Toshiba 19nm MLC | |||
Sequential Read | 3180 MB/s | 3000 MB/s | 3000 MB/s | 1500 MB/s | 2400 MB/s | |
Sequential Write | 2960 MB/s | 2100 MB/s | 2200 MB/s | 800 MB/s | 1500 MB/s | |
Random Read | 355k IOPS | 320k IOPS | ||||
Random Write | 365k IOPS | 265k IOPS | ||||
Power | Read | 4.2 W | 4.5 W | 4.9 W | 3.3 W | 5.5 W |
Write | 4.7 W | 3.4 W | 3.2 W | 6.4 W | ||
Idle | 3 mW | 3 mW | 3 mW | 5 mW | 6 mW | |
TCG Opal Encryption | Optional | No |
Aside from the upgrade to a new generation of 3D NAND, not much has changed from the XG5. The Toshiba XG6 is still using the same TC58NCP090GSB 8-channel controller as the XG5, but with another year's worth of firmware development. The use of an existing controller probably helped Toshiba get the XG6 out the door sooner and ensure they could be first to ship drives with 96L NAND, but it is possible that the XG6's performance is being held back a bit by the older controller. The controller is not really obsolete yet since it is still one of the most power-efficient NMVe controllers available, but the new in-house controller Western Digital debuted earlier this year gets more performance out of the same flash while usually offering similar power efficiency. Toshiba will need a new controller next year in order to keep the XG series in the high-end segment.
The basic layout of the XG6 has not changed from the XG5, though the power delivery components have been modified slightly, likely to accommodate the lower voltage for the NAND interface. The XG6 is another single-sided design to maximize compatibility with the thinnest notebook computers. Our 1TB sample has two NAND packages each containing eight 512Gb BiCS4 3D TLC dies. Toshiba is using 256Gb dies on at least some of the smaller capacities, but they won't say specifically whether it's just the 256GB model or also the 512GB model. Either way, it's nice that they are willing to use the slightly less cost-effective low-capacity parts for smaller drives in order retain most of the performance by keeping all 8 of the controller's channels populated.
Our XG6 came with an unusual rigid plastic label that gives it the polished appearance of a retail product, but doesn't actually serve as the heatspreader it resembles. Thanks to the power efficiency of Toshiba's controller, heat shouldn't be a problem at all.
The Competition
We don't get OEM SSDs in for review very often. Toshiba is only really sampling the XG series because it is where their 64L and 96L NAND have debuted, and they haven't had retail versions ready to sample instead. Most of the other drives we have to compare the XG6 against are retail models, but most of them have OEM counterparts based on the same hardware and similar or identical firmware. For example, the WD Black is closely related to the WD SN720 that was announced slightly earlier but wasn't sampled for review.
AnandTech 2018 Consumer SSD Testbed | |
CPU | Intel Xeon E3 1240 v5 |
Motherboard | ASRock Fatal1ty E3V5 Performance Gaming/OC |
Chipset | Intel C232 |
Memory | 4x 8GB G.SKILL Ripjaws DDR4-2400 CL15 |
Graphics | AMD Radeon HD 5450, 1920x1200@60Hz |
Software | Windows 10 x64, version 1709 |
Linux kernel version 4.14, fio version 3.6 | |
Spectre/Meltdown microcode and OS patches current as of May 2018 |
- Thanks to Intel for the Xeon E3 1240 v5 CPU
- Thanks to ASRock for the E3V5 Performance Gaming/OC
- Thanks to G.SKILL for the Ripjaws DDR4-2400 RAM
- Thanks to Corsair for the RM750 power supply, Carbide 200R case, and Hydro H60 CPU cooler
- Thanks to Quarch for the XLC Programmable Power Module and accessories
- Thanks to StarTech for providing a RK2236BKF 22U rack cabinet.
AnandTech Storage Bench - The Destroyer
The Destroyer is an extremely long test replicating the access patterns of very IO-intensive desktop usage. A detailed breakdown can be found in this article. Like real-world usage, the drives do get the occasional break that allows for some background garbage collection and flushing caches, but those idle times are limited to 25ms so that it doesn't take all week to run the test. These AnandTech Storage Bench (ATSB) tests do not involve running the actual applications that generated the workloads, so the scores are relatively insensitive to changes in CPU performance and RAM from our new testbed, but the jump to a newer version of Windows and the newer storage drivers can have an impact.
We quantify performance on this test by reporting the drive's average data throughput, the average latency of the I/O operations, and the total energy used by the drive over the course of the test.
The Toshiba XG6 is slightly faster than the XG5 on The Destroyer. It still trails behind the fastest retail SSDs but at twice the speed of a mainstream SATA drive it's well into high-end territory.
Average and 99th percentile latency have both improved for the XG6, bringing it even closer to the top of the charts and leaving only a small handful of drives that score better.
The average read latency for the XG6 is only slightly better than the XG5, which was the slowest drive in the high-end tier. For average write latency, the XG6 represents a much more substantial improvement that puts it ahead of almost every other TLC-based drive.
The XG5 already had very good QoS with 99th percentile read and write latencies that were quite low. The XG6 improves on both counts, with writes particularly improving.
The total energy usage of the XG6 over the course of The Destroyer is very slightly higher than what the XG5 required, but this tiny efficiency sacrifice is easily justified by the performance increases. Toshiba's XG series remains one of the few options for a high-performance NVMe SSD with power efficiency that is comparable to mainstream SATA drives.
AnandTech Storage Bench - Heavy
Our Heavy storage benchmark is proportionally more write-heavy than The Destroyer, but much shorter overall. The total writes in the Heavy test aren't enough to fill the drive, so performance never drops down to steady state. This test is far more representative of a power user's day to day usage, and is heavily influenced by the drive's peak performance. The Heavy workload test details can be found here. This test is run twice, once on a freshly erased drive and once after filling the drive with sequential writes.
The Toshiba XG6 brings a healthy boost to the full-drive average data rate on the Heavy test, but only improves the empty drive test run performance by about 5% over the XG5. Toshiba is definitely starting to fall behind the fastest high-end drives on this test, but the XG6 is still comfortably ahead of most entry-level NVMe products and more than twice as fast as the Crucial MX500 SATA SSD.
The Toshiba XG6 brings very small regressions to the latency scores on the empty-drive test runs, but makes up for it with substantially improved average and 99th percentile latency when the Heavy test is run on a full drive.
The slight regression in average latency for the empty drive test runs comes from an increase in average write latency. Read latency has improved substantially and write latency for the full-drive test runs doesn't stand out for the XG6 the way it did for the XG5.
For 99th percentile latency, both read and write performance are slightly worse on the XG6 than the XG5 when the Heavy test is run on an empty drive. But full-drive latency QoS has improved markedly for both read and write operations.
The Toshiba XG6 uses slightly more energy over the course of the Heavy test than the XG5 does, when the test is run on an empty drive. The improved full-drive performance helps the XG6 come out ahead on energy usage for that test run. Either way, the XG6's efficiency is comparable to SATA drives and the WD Black is the only other high-end NVMe that offers this kind of power efficiency.
AnandTech Storage Bench - Light
Our Light storage test has relatively more sequential accesses and lower queue depths than The Destroyer or the Heavy test, and it's by far the shortest test overall. It's based largely on applications that aren't highly dependent on storage performance, so this is a test more of application launch times and file load times. This test can be seen as the sum of all the little delays in daily usage, but with the idle times trimmed to 25ms it takes less than half an hour to run. Details of the Light test can be found here. As with the ATSB Heavy test, this test is run with the drive both freshly erased and empty, and after filling the drive with sequential writes.
The average data rates delivered by the Toshiba XG6 on the Light test are similar to many other high-end NVMe SSDs though clearly lower than the fastest tier of drives. As with the Heavy test, the full-drive performance is the more significant improvement from the XG5.
Average latency from the XG6 has improved for both full and empty drive test runs, but the 99th percentile latency when the Light test is run on a freshly erased drive is actually worse than the XG5.
Average read latency doesn't vary much among high-end NVMe SSDs, though there are some outliers for full-drive read latency. The XG6 doesn't have the best scores, but the improvements the XG6 brings over the XG5 help ensure it doesn't stick out even among the newest and fastest competitors. For average write latency, the improvement in full-drive performance secures the XG6 a position in the high-end tier.
The 99th percentile read latency from the XG6 is typical for a high-end SSD when the Light test is run on an empty drive but a little high when the drive is full, though it's still improved over the XG5. The 99th percentile write latency regressed significantly for the empty-drive test run, back to the level of old high-end drives or current entry-level NVMe, but the full-drive 99th percentile write latency is excellent.
The energy used by the XG6 over the course of the Light test is barely different from that used by the XG5 or the WD Black. All three are slightly less efficient than the Crucial MX500 mainstream SATA drive and some of the more efficient entry-level NVMe drives.
Random Read Performance
Our first test of random read performance uses very short bursts of operations issued one at a time with no queuing. The drives are given enough idle time between bursts to yield an overall duty cycle of 20%, so thermal throttling is impossible. Each burst consists of a total of 32MB of 4kB random reads, from a 16GB span of the disk. The total data read is 1GB.
The burst random read performance of the Toshiba XG5 was rather slow and the XG6 improves on it but not enough to bring it up to par. Intel/Micron 3D TLC seems to offer substantially lower read latency, though some other drives have managed to get better random read performance out of BiCS TLC than Toshiba's XG series.
Our sustained random read performance is similar to the random read test from our 2015 test suite: queue depths from 1 to 32 are tested, and the average performance and power efficiency across QD1, QD2 and QD4 are reported as the primary scores. Each queue depth is tested for one minute or 32GB of data transferred, whichever is shorter. After each queue depth is tested, the drive is given up to one minute to cool off so that the higher queue depths are unlikely to be affected by accumulated heat build-up. The individual read operations are again 4kB, and cover a 64GB span of the drive.
The rankings for sustained random read performance are largely similar to the burst random read test. The XG6 is improved over the XG5 but there's still quite a bit of room for improvement.
Power Efficiency in MB/s/W | Average Power in W |
The XG6 puts Toshiba back into a tie for the best power efficiency from a TLC drive performing random reads, because the middle of the road performance doesn't require all that much power—just over half the power required by the SM2262EN's class-leading performance.
While the low queue depth random read performance from the Toshiba XG6 is nothing special, it does scale up quite well and by QD32 it has caught up with the SM2262EN and pulled ahead of all other TLC drives.
Random Write Performance
Our test of random write burst performance is structured similarly to the random read burst test, but each burst is only 4MB and the total test length is 128MB. The 4kB random write operations are distributed over a 16GB span of the drive, and the operations are issued one at a time with no queuing.
The burst random write performance of the Toshiba XG6 is about 12% faster than the XG5—not enough to catch up to the fastest drives, but enough to stay above average even as the standards for high-end performance climb from year to year.
As with the sustained random read test, our sustained 4kB random write test runs for up to one minute or 32GB per queue depth, covering a 64GB span of the drive and giving the drive up to 1 minute of idle time between queue depths to allow for write caches to be flushed and for the drive to cool down.
On the longer random write test, the Toshiba XG6 places at the top of the second tier of drives. It can't match the very fastest competitors, but it beats all the more mid-range NVMe drives.
Power Efficiency in MB/s/W | Average Power in W |
The XG6 has leapfrogged the WD Black to retake the lead in power efficiency during random writes, with about a 7% performance per Watt lead. Even with the improved performance relative to the XG5, the XG6 is is still one of the least power-hungry NVMe drives during this test.
The random write performance of the XG6 scales best from QD2 to QD4 which brings it near saturation. This pattern is similar to the behavior of drives from Samsung, WD and the XG5, while the Phison and Silicon Motion controllers seem to pick up the pace a bit earlier with better QD2 performance.
Sequential Read Performance
Our first test of sequential read performance uses short bursts of 128MB, issued as 128kB operations with no queuing. The test averages performance across eight bursts for a total of 1GB of data transferred from a drive containing 16GB of data. Between each burst the drive is given enough idle time to keep the overall duty cycle at 20%.
The burst sequential read speed of the Toshiba XG6 is slightly slower than the XG5, and still middle of the road for NVMe drives. The top drives are approaching twice the QD1 performance of the XG6, so this is probably where Toshiba needs to focus the most on improving.
Our test of sustained sequential reads uses queue depths from 1 to 32, with the performance and power scores computed as the average of QD1, QD2 and QD4. Each queue depth is tested for up to one minute or 32GB transferred, from a drive containing 64GB of data. This test is run twice: once with the drive prepared by sequentially writing the test data, and again after the random write test has mixed things up, causing fragmentation inside the SSD that isn't visible to the OS. These two scores represent the two extremes of how the drive would perform under real-world usage, where wear leveling and modifications to some existing data will create some internal fragmentation that degrades performance, but usually not to the extent shown here.
The longer sequential read test including moderately higher queue depths puts the XG6 in much better light, with clear improvement over the XG5 and scores that are behind only Samsung and Silicon Motion.
Power Efficiency in MB/s/W | Average Power in W |
The power efficiency of the Toshiba XG6 during sequential reads is uncontested by anything other current drive using flash memory. It delivers 15% better performance per Watt than the SM2262EN that is tied for highest absolute performance.
The Toshiba XG5 wasn't quite able to deliver its maximum sequential read speed at QD4, but the XG6 is saturated by then and delivers more than 3GB/s. The Silicon Motion controllers scale up in performance soonest, with the HP EX920 delivering full sequential read speed at QD2 while some high-end drives don't saturate until QD16.
Sequential Write Performance
Our test of sequential write burst performance is structured identically to the sequential read burst performance test save for the direction of the data transfer. Each burst writes 128MB as 128kB operations issued at QD1, for a total of 1GB of data written to a drive containing 16GB of data.
The burst sequential write speed of the Toshiba XG6 is another slight regression relative to the XG5, but it doesn't change its standing all that much. The Samsung 970 EVO and the upcoming high-end controllers from Silicon Motion and Phison offer substantially better QD1 performance, but the XG6 is more or less tied with most of the current high-end drives like the WD Black and the HP EX920.
Our test of sustained sequential writes is structured identically to our sustained sequential read test, save for the direction of the data transfers. Queue depths range from 1 to 32 and each queue depth is tested for up to one minute or 32GB, followed by up to one minute of idle time for the drive to cool off and perform garbage collection. The test is confined to a 64GB span of the drive.
The sustained sequential write speed of the Toshiba XG6 is a substantial improvement over the XG5 and puts the XG6 very close to the top of the charts with clearly better performance than any of the BiCS3-based drives.
Power Efficiency in MB/s/W | Average Power in W |
The Toshiba XG5 was still holding on to its lead in power efficiency (among flash-based SSDs), and the XG6 runs up the score by another 5% by delivering much higher performance while still drawing less power than any competing high-end NVMe drive.
The sequential write performance of the XG6 shows some variability due to the SLC cache filling up and requiring some background work that doesn't fit within the idle time this test provides, but performance doesn't drop as much or as often as for the Phison E12, and the average at higher queue depths is still competitive with the drives that offer steadier write speeds.
Mixed Random Performance
Our test of mixed random reads and writes covers mixes varying from pure reads to pure writes at 10% increments. Each mix is tested for up to 1 minute or 32GB of data transferred. The test is conducted with a queue depth of 4, and is limited to a 64GB span of the drive. In between each mix, the drive is given idle time of up to one minute so that the overall duty cycle is 50%.
The mixed random I/O performance of the Toshiba XG6 jumps by about 47% compared to the XG5, making it competitive with most current high-end TLC drives.
Power Efficiency in MB/s/W | Average Power in W |
Thanks to the big performance boost at almost no cost in added power consumption, the Toshiba XG6 takes an 11% lead over the nearest competition in power efficiency on this test.
The Toshiba XG6 is able to increase performance throughout the test as more writes are added to the workload, with much more performance growth than the XG5 showed. The performance growth falters a bit near the end of the test but the XG6 still delivers the expected performance spike with the final phase of the test as the workload shifts to pure writes.
Mixed Sequential Performance
Our test of mixed sequential reads and writes differs from the mixed random I/O test by performing 128kB sequential accesses rather than 4kB accesses at random locations, and the sequential test is conducted at queue depth 1. The range of mixes tested is the same, and the timing and limits on data transfers are also the same as above.
The mixed sequential I/O performance of the XG6 is a bit faster than the XG5, but not enough to boost it up to the top tier of drives. The relatively poor QD1 sequential performance compared to the competition is holding back the XG6 here.
Power Efficiency in MB/s/W | Average Power in W |
In spite of mid-tier performance, the XG6 still manages very good power efficiency that is a bit better than the XG5 and not too far behind the WD Black. However, the XG6 will also soon be beat by numerous upcoming Phison E12 drives even if the latter are still using the older 64-layer Toshiba 3D TLC.
Slow QD1 read speeds are the main factor keeping the XG6 from matching the overall performance scores of the top tier of drives. The XG6 also shows a bit of performance variation during the second half of the test due to garbage collection or a full SLC cache, but the impact is not severe.
Power Management Features
Real-world client storage workloads leave SSDs idle most of the time, so the active power measurements presented earlier in this review only account for a small part of what determines a drive's suitability for battery-powered use. Especially under light use, the power efficiency of a SSD is determined mostly be how well it can save power when idle.
For many NVMe SSDs, the closely related matter of thermal management can also be important. M.2 SSDs can concentrate a lot of power in a very small space. They may also be used in locations with high ambient temperatures and poor cooling, such as tucked under a GPU on a desktop motherboard, or in a poorly-ventilated notebook.
Toshiba XG6 NVMe Power and Thermal Management Features |
|||
Controller | Toshiba TC58NCP090GSB | ||
Firmware | AGXA4001 | ||
NVMe Version |
Feature | Status | |
1.0 | Number of operational (active) power states | 3 | |
1.1 | Number of non-operational (idle) power states | 3 | |
Autonomous Power State Transition (APST) | Supported | ||
1.2 | Warning Temperature | 78°C | |
Critical Temperature | 82°C | ||
1.3 | Host Controlled Thermal Management | Supported | |
Non-Operational Power State Permissive Mode | Not Supported |
The Toshiba XG6 supports most of the NVMe power and thermal management features save for the relatively obscure and recent non-operational power state permissive mode to control background processing during idle time. The XG6 is a bit unusual in providing three idle states instead of just two, but the deepest state is probably not worth using very often due to its higher transition latency and minimal power power savings relative to the intermediate PS4 idle state.
Toshiba XG6 NVMe Power States |
|||||
Controller | Toshiba TC58NCP090GSB | ||||
Firmware | AGXA4001 | ||||
Power State |
Maximum Power |
Active/Idle | Entry Latency |
Exit Latency |
|
PS 0 | 6.0 W | Active | - | - | |
PS 1 | 2.4 W | Active | - | - | |
PS 2 | 1.9 W | Active | - | - | |
PS 3 | 50 mW | Idle | 1.5 ms | 1.5 ms | |
PS 4 | 5 mW | Idle | 6 ms | 14 ms | |
PS 5 | 3 mW | Idle | 50 ms | 80 ms |
Note that the above tables reflect only the information provided by the drive to the OS. The power and latency numbers are often very conservative estimates, but they are what the OS uses to determine which idle states to use and how long to wait before dropping to a deeper idle state.
Idle Power Measurement
SATA SSDs are tested with SATA link power management disabled to measure their active idle power draw, and with it enabled for the deeper idle power consumption score and the idle wake-up latency test. Our testbed, like any ordinary desktop system, cannot trigger the deepest DevSleep idle state.
Idle power management for NVMe SSDs is far more complicated than for SATA SSDs. NVMe SSDs can support several different idle power states, and through the Autonomous Power State Transition (APST) feature the operating system can set a drive's policy for when to drop down to a lower power state. There is typically a tradeoff in that lower-power states take longer to enter and wake up from, so the choice about what power states to use may differ for desktop and notebooks.
We report two idle power measurements. Active idle is representative of a typical desktop, where none of the advanced PCIe link or NVMe power saving features are enabled and the drive is immediately ready to process new commands. The idle power consumption metric is measured with PCIe Active State Power Management L1.2 state enabled and NVMe APST enabled if supported.
The active idle power consumption of the Toshiba XG6 is slightly higher than the XG5 but still in the normal range for high-end NVMe drives. However, Silicon Motion and Phison have both managed to reach active idle power levels that are well under 1W instead of slightly higher, so Toshiba does have some room for improvement in power efficiency. The 110mW idle power we measured is decent for a NVMe drive, but substantially higher than the Silicon Motion controllers that manage the rare feat of successfully making use of their deepest idle state even on our desktop testbed.
The idle wake-up latency of the Toshiba XG6 is substantially higher than the XG5 and is comparable to that of the Silicon Motion-based drives that lead in our idle power consumption measurements. As long as the Toshiba XG6 is no slower to wake up in a notebook system where it successfully reaches its deepest power state, this latency shouldn't be a problem. Desktop systems would probably not be using the deepest idle state very often, so the wake-up should usually be much lower than the 52ms measured here.
Conclusion
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.