Western Digital claims AI-optimized storage with new SSDs and HDD

Western Digital has defined a six-stage AI data cycle and introduced two new SSDs and a disk drive to match them.

The AI data cycle stages are (1) archives of raw data content, (2) data prep and ingest, (3) AI model training, (4) interface and prompting, (5) AI inference engine, and (6) new content generation. Stage 1 needs high-capacity disk drives. Stage 2 needs high-capacity SSDs for data lake operations. Stages 3, 4, and 5 need the same high-capacity SSDs plus high-performance compute SSDs for model training run checkpointing and caching. Stage 6 brings us back to needing high-capacity disk drives.

Rob Soderbery, Western Digital
Rob Soderbery

Rob Soderbery, EVP and GM of Western Digital’s Flash Business Unit, said: “Data is the fuel of AI. As AI technologies become embedded across virtually every industry sector, storage has become an increasingly important and dynamic component of the AI technology stack. The new AI Data Cycle framework will equip our customers to build a storage infrastructure that impacts the performance, scalability, and the deployment of AI applications.”

Western Digital is introducing three new Ultrastar-brand storage drives:

  • DC SN861 SSD for fast checkpointing and caching
  • DC SN655 SSD for the high-capacity SSD requirement
  • DC HC690 HDD for the storage of raw and new content data


This is Western Digital’s first PCIe gen 5 SSD and suited for AI training model run checkpointing. It introduced its PCIe gen 4 SN850 drive back in 2020, but this was an M.2-format drive with limited capacity: 500 GB, 1 and 2 TB. It also had an SN840 PCIe gen 3 drive in the U.2 (2.5-inch) format with 1.6 TB to 15.36 TB capacity range in 2020.

The SN861 comes in the E1.S, E3.S, and U.2 formats with up to 16 TB capacity. E1.S is like a larger version of the M.2 gumstick format. Western Digital claims the SN861 “delivers up to 3x random read performance increase versus the previous generation with ultra-low latency and incredible responsiveness for large language model (LLM) training, inferencing and AI service deployment.”

Details are slim. We don’t know the type of NAND used, but understand it to be TLC. Nor do we know the 3D NAND generation and layer count. It’s probably BiCS 6 with 162 layers but could be the newer BiCS 8 with 218 layers.

It will come in 1 and 3 drive writes per day (DWPD) variants with a five-year warranty, and supports NVMe 2.0 and OCP 2.0. The E1.S version is sampling now. The U.2 model will be sampling in July with volume shipments set for the third quarter. There is no information about the E3.S version’s availability or the E1.S volume shipment date.

New Western Digital drives


This is a high-capacity SSD. The existing PCIe gen 4-connected DC SN655 SSD with its 15.36 TB max capacity has been expanded more than fourfold to support up to 64 TB using TLC NAND in a U.3 format. The U.3 format is equivalent to U.2 in physical size and a U.3 chassis bay supports SAS, SATA, and NVMe interfaces in the same slot.

SN655 variants are sampling now and volume shipments will start later this year, with more drive details being released then.

DC HC690 disk drive

Western Digital has tweaked its DC HC680 SMR tech to lift its capacity from 28 to 32 TB. There are few details available at present and our understanding is that this is a ten-platter drive – it might be 11 – using shingled magnetic media (SMR – partially overlapping write tracks) with OptiNAND energy-assisted PMR (ePMR), and triple-stage actuator (TSA) in a helium-filled enclosure. There is an ArmorCache write cache data safety feature.

Competitor Seagate announced 30 TB conventional Exos HAMR drives in January with a 32 TB SMR HAMR drive now available as well. Western Digital has caught up to that capacity point using microwave-assisted magnetic recording (MAMR). Toshiba demonstrated a 32 TB shingled HAMR drive and a 31 TB 11-platter MAMR drive last month. Now all three HDD manufacturers are at the 32 TB SMR drive level.