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VDURA CEO’s Long Live The Short King blog

What happened

VDURA CEO Ken Claffey published a blog titled "Long Live the Short King. Now Look One Tier Down" on October 27, 2026, arguing that the SemiAnalysis realization that HBM bandwidth limitations cramp HBM capacity rises beyond 4-hi stacks also applies to NVMe SSDs used in KV Cache tiering, where write bandwidth is more important than capacity. The blog states that HBM 4/4e stacks range from 4-hi to 12-hi in capacity, but the 2,048 pin count is static, so bandwidth is the same regardless of capacity; a PCIe Gen5 x4 NVMe drive gets roughly 14 GB/s read bandwidth whether it is 7.68 TB or 61.44 TB. Citing Kioxia's CD9P PCIe Gen5 TLC SSD as an example, he points out eight times the capacity with identical write bandwidth and nine percent less read bandwidth. The blog also notes SSD terabytes cost 14x disk drive TBs, supplies a formula for the number of SSDs needed, N = R ÷ (d × E), where N is the number of drives, R is the required bandwidth, d is what one SSD delivers, and E is the fraction of d the architecture actually gets through to a client, and outlines a 5-step SSD buying guide: start with bandwidth in both directions, count devices not terabytes, take the smallest drive that gets you to N, check what capacity came along, and put the rest in a hard disk drive capacity tier. He stresses that the fall from flash to disk performance is orders of magnitude, so the capacity tier must be built for throughput, not dollars per terabyte alone. The blog mentions that VDURA's parallel file system with built-in S3 support can ingest data from the SSD tier and scales performance as capacity ramps up.