Original Link: https://www.anandtech.com/show/10296/the-sandisk-x400-1tb-ssd-review



The SanDisk X400 is the flagship model of SanDisk's business/OEM SSD lineup. As the successor to the X300 and X300s, the X400 continues the strategy of combining premium features like encryption and a 5-year warranty with the use of cheaper TLC NAND flash to hit mainstream price points.

The SanDisk X400 is intended to be a relatively high-end TLC drive with performance suitable for the mainstream segment of the SSD market that is still predominantly served by SSDs using MLC NAND. SanDisk has had success in the past with developing TLC SSDs such as the Ultra II that perform much better than they typical value-oriented TLC-based SSD.

The X400 adopts the Marvell 88SS1074 SSD controller, a made-for-TLC design with LDPC error correction support that allows for a substantial increase in rated write endurance. The NAND used in the X400 is SanDisk's "sixth generation TLC", manufactured on the 15nm process they share with Toshiba. Carried over from other TLC drives like the Ultra II, the flash in the X400 supports SanDisk's nCache 2.0 SLC caching with on-chip copying of data from the SLC cache to TLC.

Unlike most TLC product lines, the SanDisk X400 provides usable capacities at power of two increments: 128GB through 1024GB, rather than the more common 120GB through 960GB. SanDisk hails the X400 line as including the first single-sided 1TB M.2 SSD - the X300 M.2 only went up to 512GB by comparison. The 2.5" models also use a single-sided PCB, with a large thermal pad interfacing all the flash and DRAM chips and the controller to the metal side of the case.

SanDisk X400 Specifications
Capacity 128 GB 256 GB 512 GB 1 TB
(1024GB)
Sequential Read 540 MB/s 540 MB/s 540 MB/s 545 MB/s
Sequential Write 340 MB/s 520 MB/s 520 MB/s 520 MB/s
Random Read IOPS 93.5k 93.5k 93.5k 95k
Random Write IOPS 60k 60k 75k 75k
Form Factors 2.5", M.2 2280
Encryption TCG Opal 2.0 (SED models only)
Write Endurance 72 TB 80 TB 160 TB 320 TB
Warranty 5 years
DWPD Equivalent 0.315 0.175

The SanDisk X300s was the self-encrypting drive variant of the X300, but for the X400 SanDisk is using the same branding on both variants. The self-encrypting drive models have separate SKUs but are still advertised as just SanDisk X400, not X400s. This makes it a little confusing all around and means that users should double check the exact SKU being offered. In the table below, 1122 in the SKU name indicates an individual unit per sale with retail packaging, rather than bulk purchase packaging.

    Self-Encrypting SKU Regular SKU
128 GB M.2   SD8SN8U-128G-1122
SD8SN8U-128G 
SATA SD8TB8U-128G-1122 SD8SB8U-128G-1122 
SD8SB8U-128G
256 GB M.2   SD8SN8U-256G-1122
SD8SN8U-256G 
SATA SD8TB8U-256G-1122 SD8SB8U-256G-1122 
SD8SB8U-256G 
512 GB M.2   SD8SN8U-512G-1122
SD8SN8U-512G
SATA SD8TB8U-512G-1122 SD8SB8U-512G-1122
SD8SB8U-512G 
1TiB (1024GB) M.2   SD8SN8U-1T00-1122
SD8SN8U-1T00
SATA SD8TB8U-1T00-1122 SD8SB8U-1T00-1122 
SD8SB8U-1T00

In this review, we are testing the 2.5" 1TB SanDisk X400 model with no TCG Opal encryption support, the SD8SB8U-1T00-1122. The competition and drives to compare against includes the OCZ Trion 150 as one of the best-performing budget TLC SSDs, the Crucial MX200 (a solid mid-range MLC SSD), SanDisk's own high-end MLC-based Extreme Pro, and the Samsung 850 EVO (the 3D TLC SSD that performs like a high-end MLC SSD).

AnandTech 2015 SSD Test System
CPU Intel Core i7-4770K running at 3.5GHz
(Turbo & EIST enabled, C-states disabled)
Motherboard ASUS Z97 Pro (BIOS 2701)
Chipset Intel Z97
Memory Corsair Vengeance DDR3-1866 2x8GB (9-10-9-27 2T)
Graphics Intel HD Graphics 4600
Desktop Resolution 1920 x 1200
OS Windows 8.1 x64


Performance Consistency

Our performance consistency test explores the extent to which a drive can reliably sustain performance during a long-duration random write test. Specifications for consumer drives typically list peak performance numbers only attainable in ideal conditions. The performance in a worst-case scenario can be drastically different as over the course of a long test, as drives can run out of spare area and have to start performing garbage collection as well as sometimes even reach power or thermal limits.

In addition to an overall decline in performance, a long test can show patterns in how performance varies on shorter timescales. Some drives will exhibit very little variance in performance from second to second, while others will show massive drops in performance during each garbage collection cycle but otherwise maintain good performance, and others show constantly wide variance. If a drive periodically slows to hard drive levels of performance, it may feel slow to use even if its overall average performance is very high.

To maximally stress the drive's controller and force it to perform garbage collection and wear leveling, this test conducts 4kB random writes with a queue depth of 32. The drive is filled before the start of the test, and the test duration is one hour. Any spare area will be exhausted early in the test and by the end of the hour even the largest drives with the most overprovisioning will have reached a steady state. We use the last 400 seconds of the test to score the drive both on steady-state average writes per second and on its performance divided by the standard deviation.

Steady-State 4KB Random Write Performance

The X400's steady-state write performance is unimpressive but typical for planar TLC drives.

Steady-State 4KB Random Write Consistency

The consistency score of the X400 is good but not great, and it is again close to the OCZ Trion 150.

IOPS over time
Default
25% Over-Provisioning

The X400 does not display an initial burst of extreme performance and instead wobbles around 20k IOPS before dropping down to steady state. The X400 does not exhibit severe stalling at any stage of the test, whereas the previously reviewed Trion 150 handles the transition to steady state poorly.

Steady-State IOPS over time
Default
25% Over-Provisioning

In steady-state the X400's performance is not tightly regulated but doesn't have any outliers of significantly below-average performance. Extra overprovisioning does little to improve the worst-case performance but greatly increases the average and best-case write performance.



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 and unlike our Iometer tests, 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.

We quantify performance on this test by reporting the drive's average data throughput, a few data points about its latency, and the total energy used by the drive over the course of the test.

AnandTech Storage Bench - The Destroyer (Data Rate)

The X400's average data rate on The Destroyer places it clearly ahead of the other planar TLC drives and on par with the Crucial MX200.

AnandTech Storage Bench - The Destroyer (Latency)

The average service time for the X400 doesn't quite compete against the MLC drives, but it does put the X400 clearly ahead of the budget TLC drives.

AnandTech Storage Bench - The Destroyer (Latency)

The X400's latency outliers at the 10ms threshold again put it ahead of the budget drives but also clearly behind the MLC drives and the Samsung 850 EVO.

AnandTech Storage Bench - The Destroyer (Latency)

At the 100ms threshold for latency outliers most drives in this roundup score very close to each other, and the X400 is a little slower than average.

AnandTech Storage Bench - The Destroyer (Power)

The X400's power usage over the course of The Destroyer is pretty good, especially for a TLC drive. Most of the faster drives sacrifice some efficiency.



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.

AnandTech Storage Bench - Heavy (Data Rate)

Unlike on The Destroyer, the X400 can't quite keep pace with the Crucial MX200 or other MLC drives on the Heavy test, but it is still faster than the other planar TLC drives.

AnandTech Storage Bench - Heavy (Latency)

The average service time of the SanDisk X400 on the Heavy test is the best among planar TLC drives, but the TLC drives are all still at the bottom of the ranking by comparison.

AnandTech Storage Bench - Heavy (Latency)

The number of latency outliers experienced by the X400 puts it in the same class as the other planar TLC drives, while most of the MLC drives have much tighter control on latency.

AnandTech Storage Bench - Heavy (Power)

As with The Destroyer, the X400 comes in third place for power consumption and overall efficiency, behind the Crucial BX100 and MX200. This is impressive given how write-intensive the Heavy test is and how the the higher power consumption of TLC flash is usually most apparent for write operations.



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.

AnandTech Storage Bench - Light (Data Rate)

The scores on the Light test are not spread as widely as for the more intense ATSB tests, and the SLC caching capabilities of several of the drives come in handy. The X400's average data rate puts it in the middle of the pack, but its good full-drive performance distinguishes it from the other planar TLC drives and makes it tied against several MLC drives.

AnandTech Storage Bench - Light (Latency)

The average service time of the X400 is slightly worse than average for this bunch of drives, and it isn't able to score a clear win against any MLC drives on this metric.

AnandTech Storage Bench - Light (Latency)

The latency outliers above 10ms highlight the planar TLC drives as slower than most MLC drives, but the X400 doesn't do a particularly bad job of keeping latency low.

AnandTech Storage Bench - Light (Power)

Once again the X400 comes in third for overall power efficiency (almost tied for second place), and this time there is a fairly clear gap between it and fourth place.



Random Read Performance

The random read test requests 4kB blocks and tests queue depths ranging from 1 to 32. The queue depth is doubled every three minutes, for a total test duration of 18 minutes. The test spans the entire drive, which is filled before the test starts. The primary score we report is an average of performances at queue depths 1, 2 and 4, as client usage typically consists mostly of low queue depth operations.

Iometer - 4KB Random Read

The X400's random read performance is almost as good as the Samsung 850 EVO and much better than the other planar TLC drives. This is a significant accomplishment, as random reads are often the slowest operation for TLC drives and hard to improve with caching.

Iometer - 4KB Random Read (Power)

The X400's mid-range random read performance is achieved with relatively low power consumption, making it surprisingly efficient for a TLC drive.

At the highest queue depths the X400 can't quite reach the limits of the fastest drives, but overall the scaling of both performance and power usage are reasonable for a mid-range SATA drive.

Random Write Performance

The random write test writes 4kB blocks and tests queue depths ranging from 1 to 32. The queue depth is doubled every three minutes, for a total test duration of 18 minutes. The test is limited to a 16GB portion of the drive, and the drive is empty save for the 16GB test file. The primary score we report is an average of performances at queue depths 1, 2 and 4, as client usage typically consists mostly of low queue depth operations.

Iometer - 4KB Random Write

The X400's low queue depth random write speeds fall in the middle of the gap between the slowest MLC drive and the rest of the planar TLC drives.

Iometer - 4KB Random Write (Power)

The X400's power consumption is low, but with performance well behind any MLC drive the efficiency is only better than the other planar TLC drives.

The SanDisk X400's random write speeds show almost no scaling with increased queue depths, behavior that is typical of low-end TLC drives. The QD1 performance is as good as any SATA drive and while the OCZ Trion 150 hits great speeds at QD16 and QD32, the SanDisk X400 is clearly faster for the more realistic lower queue depths.



Sequential Read Performance

The sequential read test requests 128kB blocks and tests queue depths ranging from 1 to 32. The queue depth is doubled every three minutes, for a total test duration of 18 minutes. The test spans the entire drive, and the drive is filled before the test begins. The primary score we report is an average of performances at queue depths 1, 2 and 4, as client usage typically consists mostly of low queue depth operations.

Iometer - 128KB Sequential Read

The SanDisk X400 is in a three-way tie for first place for low queue depth sequential read speeds, with measurably better performance than any other TLC drive, even the Samsung 850 EVO.

Iometer - 128KB Sequential Read (Power)

The X400's power consumption is about average, but significantly better than the other two top performers. It's nowhere near the efficiency of the Crucial BX100, but for a TLC drive it's impressive.

The SanDisk X400 is one of only four drives that delivers over 500MB/s at QD1, and it's the least power-hungry of that club. At higher queue depths many other drives are able to reach the same SATA speed limit and some do it with less power consumption than the X400.

Sequential Write Performance

The sequential write test writes 128kB blocks and tests queue depths ranging from 1 to 32. The queue depth is doubled every three minutes, for a total test duration of 18 minutes. The test spans the entire drive, and the drive is filled before the test begins. The primary score we report is an average of performances at queue depths 1, 2 and 4, as client usage typically consists mostly of low queue depth operations.

Iometer - 128KB Sequential Write

The sequential write speed of the SanDisk X400 is the second test on which it is clearly slower than another planar TLC drive: the OCZ Trion 150. Both are much faster than the other two planar TLC drives in this bunch, but are slower than the MLC drives by a similarly large margin.

Iometer - 128KB Sequential Write (Power)

The X400 draws the least power of any drive on this test, so at least it's still very efficient for a TLC drive.

Sequential write performance and power consumption for the X400 are essentially constant across all queue depths, while the faster drives see at least some improvement from QD1 to QD2.



Mixed Random Read/Write Performance

The mixed random I/O benchmark starts with a pure read test and gradually increases the proportion of writes, finishing with pure writes. The queue depth is 3 for the entire test and each subtest lasts for 3 minutes, for a total test duration of 18 minutes. As with the pure random write test, this test is restricted to a 16GB span of the drive, which is empty save for the 16GB test file.

Iometer - Mixed 4KB Random Read/Write

The mixed random I/O performance of the X400 is in the middle of the pack, slightly ahead of the MLC-based OCZ Vector 180 and significantly faster than the other three planar TLC drives.

Iometer - Mixed 4KB Random Read/Write (Power)

The X400 is once again the most power efficient planar TLC drive by a wide margin, and also ahead of a few of the MLC drives.

As the proportion of writes increases, the X400's power consumption grows quite slowly. Performance does suffer in the middle of the test and the spike at the end when the test shifts to pure writes is smaller than for the MLC drives and the 850 EVO.

Mixed Sequential Read/Write Performance

The mixed sequential access test covers the entire span of the drive and uses a queue depth of one. It starts with a pure read test and gradually increases the proportion of writes, finishing with pure writes. Each subtest lasts for 3 minutes, for a total test duration of 18 minutes. The drive is filled before the test starts.

Iometer - Mixed 128KB Sequential Read/Write

The mixed sequential I/O performance of the SanDisk X400 is not able to match any of the MLC drives, but is still comfortably ahead of the other planar TLC drives.

Iometer - Mixed 128KB Sequential Read/Write (Power)

Average power consumption on the mixed sequential test is lower than everything other than the Crucial BX100, and the SanDisk X400 manages to tie the Vector 180 for efficiency, but otherwise it stands above only the other planar TLC drives.

The performance and power curves for the SanDisk X400 are very similar to the SanDisk Extreme Pro except in the pure-write phase at the end of the test, where the X400's performance cannot come close to any of the MLC drives. The X400 beats the OCZ Trion 150 overall because its high read speed outweighs the write speed advantage of the Trion 150.



ATTO

ATTO's Disk Benchmark is a quick and easy freeware tool to measure drive performance across various transfer sizes.

ATTO Performance

Aside from the write speeds that lag behind read speeds by a larger than normal margin, the ATTO results are reasonable and do not show signs of any major problems.

AS-SSD

AS-SSD is another quick and free benchmark tool. It uses incompressible data for all of its tests, making it an easy way to keep an eye on which drives are relying on transparent data compression. The short duration of the test makes it a decent indicator of peak drive performance.

Incompressible Sequential Read PerformanceIncompressible Sequential Write Performance

None of these drives show any meaningful difference in AS-SSD sequential read speed, but the write speed limitations of the X400 do show up clearly on this test.

Idle Power Consumption

Since the ATSB tests based on real-world usage cut idle times short to 25ms, their power consumption scores paint an inaccurate picture of the relative suitability of drives for mobile use. During real-world client use, a solid state drive will spend far more time idle than actively processing commands. Our testbed doesn't support the deepest DevSlp power saving mode that SATA drives can implement, but we can measure the power usage in the intermediate slumber state where both the host and device ends of the SATA link enter a low-power state and the drive is free to engage its internal power savings measures.

We also report the drive's idle power consumption while the SATA link is active and not in any power saving state. Drives are required to be able to wake from the slumber state in under 10 milliseconds, but that still leaves plenty of room for them to add latency to a burst of I/O. Because of this, many desktops default to either not using SATA Aggressive Link Power Management (ALPM) at all or to only enable it partially without making use of the device-initiated power management (DIPM) capability. Additionally, SATA Hot-Swap is incompatible with the use of DIPM, so our SSD testbed usually has DIPM turned off during performance testing.

Idle Power Consumption (HIPM+DIPM)
Active Idle Power Consumption (No ALPM)

Slumber power drawn by the X400 is not quite the lowest but is still pretty good, but active idle power is twice as high as the OCZ Trion 150 based on the Toshiba TC58/Phison S10 controller platform.



Final Words

The SanDisk X400 is intended to be a high-end TLC SSD, and there aren't many of those to compare against. The Samsung 850 EVO is without question the fastest SATA SSD using TLC NAND, and for the most part it ranks as a high-end drive even when compared with SATA SSDs in general, not just drives with TLC NAND. Aside from that, most TLC SSDs are value-oriented SSDs that sacrifice much to reach the lowest possible prices. The SanDisk X400 is not one of those products.

On almost every test the SanDisk X400 is considerably faster than the next fastest drive with planar TLC NAND. The few occasions where the OCZ Trion 150 beats the SanDisk X400, in write performance, they are balanced by several tests where the X400 ties or beats MLC drives like the Crucial MX200 or OCZ Vector 180. The only notable performance weakness is sequential write speed, but this is not a severe handicap.

In addition to raising the bar for planar TLC performance, the SanDisk X400 sets a new standard for power efficiency of drives using TLC NAND. It routinely ties or beats at least a few MLC SSDs for power efficiency, especially when its performance is not lagging far behind.

With solid performance and power efficiency and a 5-year warranty on a generous write endurance rating, the SanDisk X400 has every right to ask a higher price than any other planar TLC SSD. The warranty and endurance rating also exceed that of some low-end MLC drives that don't have much performance advantage over the X400.

At the moment the SanDisk X400 is priced at or below the OCZ Trion 150 for most capacities, especially the 512GB that is one of the cheapest SSDs in its capacity class. At 1TB perhaps the most interesting comparison is against the Mushkin Reactor, still by far the cheapest 1TB MLC SSD. The Reactor is about $25 cheaper but only has a 3-year warranty and less than half the write endurance rating. Supply of the Crucial MX200 is drying up in advance of the MX300 launch, so there are not a lot of MLC drives priced close to the X400. Overall the X400 is a reasonable step up from the cheapest budget SSDs and priced far enough below drives like the Samsung 850 EVO to not be overshadowed.

SSD Price Comparison
Drive 960GB
1TB
480GB
512GB
240GB
256GB
120GB
128GB
OCZ Trion 150 $243.49 $129.98 $59.99 $43.74
SanDisk Ultra II $225.25 $120.99 $73.48 $54.60
SanDisk X400 $244.95 $113.99 $78.93 $46.99
SanDisk Extreme Pro $348.99 $184.20 $108.00  
Crucial MX200 Sold Out $139.00 $81.72  
PNY CS2211 $289.99 $139.99 $69.99  
Mushkin Reactor $219.99 $149.99 $79.99  
Samsung 850 EVO $324.99 $149.99 $90.19 $66.75

It is refreshing to see a TLC drive that provides progress on something other than price. The X400 is a credible mid-range SSD that achieves SanDisk's goals and proves that even planar TLC NAND can compete for the mainstream segment.

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