- Sandisk’s 256TB SSD skiing completely over cache and raising concerns for short -loaded work load performance
- Allegations of faster speeds do not remain verified without public benchmarks or IOPS -benefit numbers
- Direct Write QLC can sacrifice speed in exchange for higher reliability and data integrity
Sandisk has announced a 256TB SSD, Ultraqlc SN670, which is set to be sent in the first half of 2026.
This model represents the largest SSD ever revealed by the business, marking a fat step towards the storage of high density tailored to AI and Hyperscale infrastructure.
Although the company plans to release the 128TB version for testers within weeks, full commercial accessibility remains away.
An architecture built to scale, not speed
In its core, the SN670 is built on a 218-layer BICS 3D NAND architecture and has a CBA (CMOS that is directly tied to array) 2TB die.
It is connected via a PCIe Gen5 NVME interface and is part of SanDisk’s new Ultraqlc platform.
Unlike conventional SSDs that buffer data through pseudo-SLC caches, this model uses a “direct writing QLC” approach.
This simplifies the writing process and makes the driven more power loss safe, but it also introduces trade-offs, especially when it comes to performance under heavy or short burst loads.
Without a SLC cache, the SN670 can suffer from slower cards writing, inconsistent performance under load and increased controller requirements, making the less responsive under intensive or unpredictable workload.
However, SanDisk claims that SN670 delivers over 68% faster random readings and 55% faster random writing compared to a leading 128 TB Gen 5 QLC SSD.
The sequential reading speeds are over 7% better, while sequential writing speeds are improved by more than 27% in internal comparisons.
SanDisk has underlined benefits such as dynamic frequency scaling, which is said to improve the benefit by up to 10 percent at the same effect level
It also claims that the data storage profile could reduce recycling wear by up to 33%.
Both functions are intended to improve life and reduce energy consumption.
However, none of these claims are supported by revealed performance data such as reading/writing speeds or endurance figures.
Internally, Ultraqlc SN670 is supported by a custom controller and firmware, which SanDisk says enables better latency and bandwidth, but without actual benchmarks or IOPS comparisons, these statements remain marketed projections.
It is worth noting previous iterations of SanDisk’s business drive using QLC Nand showed limitations compared to TLC-based models.
In this case, native QLC programming lates could reach 800–1200 microseconds, several times slower than SLC-based designs.
Sandisk may depend on optimizations such as large DRAM buffers or advanced DIE parallelism, but such architectural details have not yet been confirmed.
The final product originally arrives in the U.2 form, with several variants expected later in 2026.
For the time being, Sandisk’s 256TB is driving a symbolic leap towards future data infrastructure, not a realistic option for mainstream users.
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