`badblocks -w` cycles through 4 patterns (0xaa, 0x55, 0xff, 0x00),
each with a write phase + a verify phase = 8 phases. The output's
"XX% done" lines are per-phase, so the dashboard appeared to "rewind"
every ~2 hours. Two drives racing each other could look 4× apart in
displayed progress despite identical hardware — actually one was
just further into a later phase.
New _BadblocksProgress state machine watches for "Testing with
pattern 0xXX" and "Reading and comparing" headers, advances the
phase counter, and reports overall = ((phase-1) * 100 + phase_pct) / 8
clipped to 99. Pure state machine, no I/O.
7 new tests cover phase-header detection, boundary math, monotonicity
across a synthetic stream, and the original "two drives at same
per-phase % look identical" bug.
Image rebuilt and tagged but NOT deployed to the running container —
4 surface-validate jobs are 20-95% through 14TB drives and a recreate
would SIGHUP the remote badblocks processes. Deploy with
`docker compose up -d` after the current batch finishes.
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