Sandisk reveals monstrous 256TB SSD for AI, skipping cache and raising serious questions about speed under pressure
- Sandisk’s 256TB SSD skips cache entirely, raising concerns about short-burst workload performance
- Claims of faster speeds remain unverified without public benchmarks or IOPS performance numbers
- Direct Write QLC may sacrifice speed in exchange for higher reliability and data integrity
Sandisk has announced a 256TB SSD, the UltraQLC SN670, which is set to ship in the first half of 2026.
This model represents the largest SSD ever revealed by the company, marking a bold step toward high-density storage solutions tailored for AI and hyperscale infrastructure.
Although the company plans to release the 128TB version to testers within weeks, full commercial availability remains months away.
An architecture built for scale, not speed
At its core, the SN670 is built on a 218-layer BiCS 3D NAND architecture and features a CBA (CMOS directly Bonded to Array) 2Tb die.
It connects through 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 Write QLC” approach.
This simplifies the writing process and makes the drive more power-loss safe, but it also introduces tradeoffs, especially when it comes to performance under heavy or short-burst loads.
Without an SLC cache, the SN670 may suffer from slower short-burst writes, inconsistent performance under load, and increased controller demands, making it less responsive during intensive or unpredictable workloads.
However, Sandisk claims the SN670 delivers over 68% faster random reads and 55% faster random writes compared to a leading 128 TB Gen 5 QLC SSD.
The sequential read speeds are over 7% better, while sequential write speeds improve by more than 27% in internal comparisons.
Sandisk has emphasized benefits like Dynamic Frequency Scaling, which is said to improve performance by up to 10 percent at the same power level
It also claims the Data Retention profile could reduce recycling wear by as much as 33%.
Both features are intended to enhance longevity and reduce energy consumption.
However, none of these claims are backed by disclosed performance data such as read/write speeds or endurance figures.
Internally, the 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 marketing-driven projections.
It is worth noting earlier iterations of Sandisk’s enterprise drives using QLC NAND showed limitations compared to TLC-based models.
In this case, native QLC programming latencies could reach 800–1200 microseconds, several times slower than SLC-based designs.
Sandisk may be relying on optimizations like large DRAM buffers or advanced die parallelism, but such architectural details have yet to be confirmed.
The final product will arrive in U.2 form initially, with more variants expected later in 2026.
For now, Sandisk’s 256TB drive is a symbolic leap toward future data infrastructure, not a realistic option for mainstream users.
Via Blocks and Files
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