fleet operations

On an HBM part ECC costs almost nothing; on a GDDR part about 6% of capacity and bandwidth. What it buys is the difference between a corrected bit and a silently flipped exponent that turns 1.0 into infinity across a 512-GPU all-reduce. The mechanisms, the signals, and the expected-loss arithmetic.

A driver upgrade touches every layer at once: kernel module, CUDA runtime, container toolkit, NCCL, fabric driver, and every job's image. The compatibility matrix that decides whether a job can run on the new node, the canary that proves it, the wave arithmetic for 2,000 nodes, and the rehearsed rollback.

A published run gives the numbers directly: 419 unexpected interruptions in 54 days on 16,384 GPUs, and about three quarters of them hardware. What that implies per GPU-hour, which components dominate, and why a fleet above a few thousand GPUs must treat failure as routine rather than exceptional.