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SanDisk X400 1TB SSD Review

Our Verdict

The SanDisk X400 is the fastest consumer SSD we've tested with the Marvell Dean controller. Some users have already purchased the drive and really like the performance. We found it comes very close to the gold standard 850 EVO in performance, but at the same time, we question the long-term reliability of the launch firmware. Hopefully, this is an issue SanDisk can address, and you will not experience similar data loss.


  • High performance
  • Excellent pricing
  • High sustained sequential write speed


  • Questionable reliability with launch firmware
  • Average endurance ratings
  • Poor product naming with SED and non-SED models

Specifications And Features

SanDisk designed its X-Series products primarily for business notebook upgrades. SanDisk has an aggressive strategy and retail partners in place to aid businesses making the transition from disk to flash. Like the X300 Series it replaces, the X400 has become so attractive that the channel and end-users have adopted the drive as a low-cost alternative to Samsung's 850 EVO.

It's no secret that SanDisk hit a rough patch in its consumer SSD release schedule; it's been two years since the company released the Extreme Pro, which some regard as the best consumer SATA 6Gbps SSD ever released. Still, premium high-performance SSDs have moved on. SanDisk's tier one (and even tier two) competitors all have NVMe products shipping, and the tier three companies are not far behind.

SanDisk went another direction recently. Nearly all of the consumer products moved to X3 Technology (3-bit per cell) as TLC flash moved up the food chain from true entry-level products to the mainstream. The previous-generation X300 was very similar to the Extreme Pro and offered nearly the same performance, but SanDisk's vision for the SATA consumer market is all 3-bit per cell (TLC) flash. 

Technical Specifications

The SanDisk X400 ships in four capacities that range from 128GB to 1TB (1024GB), and it comes in both 2.5-inch and M.2 2280 (single-sided) form factors. So far, that is eight separate product SKUs under the X400 name, but there are four more for self-encrypted (SED) models. The X300 / X300s series designated the self-encrypted SSDs by the letter 'S' on the end, but with the new series the encrypted models just fall under the normal X400 naming convention. SanDisk only extended the encryption option to the 2.5-inch form factor SSDs.

We have a stack of new SSDs with the new LDPC-enabled Marvell 88SS1074 "Dean" controller that SanDisk uses with the X400. Behind the scenes, we built comparative charts of the products with the new controller and found the X400 leading the Marvell class in performance. SanDisk has a long history of building very good firmware for Marvell controllers. Several award-winning products, like the Extreme II and Extreme Pro, shipped with Marvell controllers running custom SanDisk firmware. We have a number of high- and low-profile products on hand to test, including the new MX300 with Micron 3D. We can say the X400 is faster than they all are.

The latest iteration of nCache 2.0 helps boost the performance of SanDisk's X3 flash. SanDisk now bundles the nCache 2.0 SLC caching algorithm with DataGuard and low-density parity check (LDPC) error correction. The technologies combine to increase write performance and data integrity.

Performance specifications rarely equate to real-world SSD performance. The X400 shares the same specifications as many other products on the market, but we often find that not all SSDs are created equal. We will examine the X400's performance in detail later in the review. 

Pricing, Warranty And Accessories

2.5-InchSD8SB8U-128G / $59.99SD8SB8U-256G / $79.99SD8SB8U-512G / $129.99SD8SB8U-1T00 / $239.99
2.5-Inch SEDSD8TB8U-128G / $49.82SD8TB8U-256G / $81.08SD8TB8U-512G / $145.64SD8TB8U-1T00 / $257.23
M.2 2280SD8SN8U-128G / $49.99SD8SN8U-256G / $87.99SD8SN8U-512G / $139.99SD8SN8U-1T00 / $247.99

We have twelve separate product SKUs under the microscope, so we built a chart to keep the information sorted. We listed each SKU next to the price, which came from Newegg, Newegg Business and Provantage. We couldn't find a single reseller that has every model in stock. As you can see, the pricing difference is nominal for each capacity point. I'm not sure why SanDisk would bother to eliminate the self-encryption feature on some products unless the Marvell Dean controller delivers less performance with encryption enabled. Products from Samsung, as well as several others, support SED features on mainstream and some entry-level products.

All twelve models come with a 5-year limited warranty. The "limited" designation indicates that the warranty is void if the user writes more data to the SSD than the specified TBW rating.

Software Package

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The X400 works with SanDisk's Dashboard. The software enables a multitude of monitoring and management features, but some of the functions will not work inside Windows 10, so keep a thumb drive available. The software will format and partition the thumb drive with the code needed to enable performance-boosting functions, such as secure erasing the SSD outside of the operating system.

A Closer Look

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Our early sample arrived as a bare drive, so we didn't get to evaluate the channel packaging. The X400 features a plastic case with a full length, single-sided PCB inside. A thermal pad rests between the components and the case exterior, but we're not sold on the thermal dissipation properties of ABS plastic.

The drive itself comes in a 2.5-inch and M.2 2280 form factor. We have the 7mm Z-height 2.5-inch model for evaluation. It shouldn't surprise anyone that this is another black rectangle SSD, just like the hundreds that came before it.

A Look Under The Hood

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SanDisk stuffed all of the surface mount components on one side of the circuit board. The design helps with manufacturing tooling and costs. It also ensures that the components spread out heat, rather than having two components on opposite sides of the PCB working to create hot spots. The controller and DRAM generate more heat than the NAND flash.

The 1TB 2.5-inch drive we are testing today is the fastest product in the X400 family, but the M.2 model shares the same performance specifications. It features half of the DRAM so that all of the components fit on a single sided M.2 2280 form factor board. In theory, the M.2 drive will slow down slightly under heavy workloads. SanDisk did not design these drives for steady-state workloads, and we don't expect users to pound the drive with enterprise workloads. 


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